Metalsmithing: If there were a book of 268,000 words written on plates of brass or gold, how much would it weigh?

The big issue here is the language written on those plates. English is a language that takes up much more space to say the same thing as other languages. So what may take 268,000 english words may take half as many characters in another language. I would suggest editing the question to include the language of the book for better answers. I'll update mine at that time.

No one else seems to have addressed the "Also, has any such book from antiquity ever been found?" part of the question, so: Yes, several. A few examples: The oldest known surviving book in the world (bound set of individual pages, as opposed to a continuous scroll) is six sheets of 24 carat gold inscribed in Etruscan (http://news.bbc.co.uk/2/hi/europe/2939362.stm). The Dead Sea Scrolls include an unusual non-religious text written on linked sheets of copper (http://www.usc.edu/dept/LAS/wsrp/educational_site/dead_sea_scrolls/copperscroll.shtml) King Darius of Persia had the details of his empire at the time inscribed on gold and silver plates to be sealed in the corner stones of the Apadana palace at Persepolis (http://en.wikipedia.org/wiki/Persepolis#Apadana_Palace) and that sort of thing seems not have been terribly unusual for the time (https://www.ideals.illinois.edu/bitstream/handle/2142/3826/gslisoccasionalpv00000i00157.pdf).

That's a good question and the weight can easily be calculated.   The plates were said to be 6 to 7 inches wide, about 8 inches long and 4 to 6 inches thick.   If they were a block of those dimensions made out of pure gold (which is unlikely and not supported by the LDS Church), they would weigh north of 140 pounds.   But eyewitness accounts state that they only weighed about 40 - 60 pounds, so regardless of whether they were real, faked or imaginary, they were not made of gold.   Curiously, brass has a density that is less than half that of gold and plates made of brass would only weigh about 60 pounds.   But brass tarnishes, so how did they stay fresh buried in the ground for 1400 years?   It's another miracle -- except if the brass in question were not actually ancient and buried in the ground for 1400 years.  If it were fresh, or gold plated in some way, then it might be tarnish free. Some LDS apologists favor Tumbaga as the metal of the golden plates.  What is Tumbaga?   It's a non-specific alloy of gold and copper that was commonly encountered by the Conquistadors in the America's.  It's non-specific because the pre-Columbian Indians didn't refine or alloy metals.   Whatever percentage copper was mixed in the gold ore, stayed there.  But if the copper content was high, then the Tumbaga plates would be less dense than pure gold plates and still have a gold appearance.   Very little Tumbaga is still around because the Spaniards melted down whatever they took and separated the copper out.   No modern Saint has the money or willingness to monkey around with a modern Tumbaga alloy to see how it behaves, but it doesn't tarnish very much if the copper content is low. It turns out you don't need to have much gold in the alloy to still get a yellowish golden looking metal.   According to this chart, an alloy of 1/3 Cu, 1/3 Ag and 1/3 Au would still do the trick. A much better material to make the plates out of, if the Nephites had access to modern materials and methods, would be laser-etched, gold anodized aluminum, like you see below.   This material could easily pack tiny font characters onto thin, tarnish proof plates, leaving behind blackened and easily readable letters as the golden plates are said to have sported.   Unfortunately, to do this the Nephites would have needed the ability to refine and work aluminum, electricity, lasers, and computers. As a tangent to this question, consider if it is possible to even squeeze a book the length of the BoM onto a stack of plates of the above dimensions.  The pages were said to be somewhat pliable and rather thin, like parchment and if made of aluminum or brass that would be less than .020" using today's modern gauges and that's a bunch of pages.     Of course, if you take out the many thousands of needless repetitions of the phrase "And it came to pass" that appear in the BoM, you need a heckuva lot fewer plates to squeeze the rest in. Seriously, as an exercise I did a little experiment.  I took the whole BoM text and removed all the verses, cross referencing, page breaks etc. and I shrunk it all down to 8 pt font in a condensed line format in a 7" by 8" size like the golden plates and chose narrow margins.   This really squeezed the thing down to almost unreadable size but it got the page count down to 258 pages, or 129 sheets if we assume both sides of each plate were engraved.   Now, if the plates were the thickness of 12 pt cardstock paper, you could squeeze all the english BoM into about 1.5" inch thick stack of paper plates of the purported dimensions.   The original stack of metal plates is said to have been about 4" to 6" thick and of course 2/3rds of them were sealed, so the translated portion has to fit in a stack no more than about 1.5" to 2" inches thick.   So far, we're doing okay IF the plates were the thickness of cardstock paper.  But they really couldn't have been that thin and still be workable on both sides of the plate because the carving or stamping would deform the plate through to the other side.  (I'm assuming that the ancient Nephites couldn't laser-etch the plates.)  So in reality they'd have to be thicker than cardstock paper. The question then becomes how thin can you make metal plate?  It turns out that today you can buy sheets of Jewelers' Bronze and Brass plate in .010 and .020 " sheets and if you cut them to size and stack them, they would make a nice little faux BoM about 1.25 to 2.5 inches thick, depending on which gauge you chose.   With the thinner gauge, you would have metal that probably could NOT be engraved on both sides.  It's so thin that it can be cut with scissors and it folds and bends easily (which matches the eyewitness descriptions but is almost impossible to engrave on).  So you'd need to go to .020" sheet at least and your BoM becomes at least 2.5" thick, probably more.   And bear in mind that gold, of any purity, is a heckuvalot softer than either jeweler's bronze or brass.  It would have very little structural rigidity at that thickness, probably less than paper.   I don't know, because I can't afford to buy jewelers gold sheet of that thickness.  20 gauge hard jewelers gold sheets in only 9 karat purity in the reputed size of the Bof M would cost about $5700 PER PAGE in today's market, or $2.2 million total if melted down. The only way to squeeze the text back down to a size that would fit in 1.5" would be to assume it was written in some ideographic script that takes up less space than English.  If we assume the existence of an extremely compact "Reformed Egyptian" that was 60 to 70%  the size of english when written, then it seems to me that this thought experiment is just barely possible.  The BoM as we know it could fit on a perfectly formed plates of the dimensions described.  Of course, no one knows what kind of language this "Reformed Eqyptian" was, if it existed at all.   We do know that the characters copied onto the "Anton sample parchments" (as they exist today) are undecipherable gobbledy-gook and not tremendously compact in their appearance.  In fact, they don't appear to resemble an ideographic script at all, but rather an alphabetic or syllabic script.   As another experiment, I sorted the characters found on the Anton transcript into similar shapes and I found that there are only about 60-70 separate characters on the Anton sample, about 30 of which resemble English letters, numbers and symbols and repeat many times over. Logographic scripts like Chinese tend to contain many thousands of characters which repeat infrequently.   Alphabetic or syllabic scripts contain many fewer characters which repeat frequently in order to construct whole words and thoughts.   The GP script appears to be either alphabetic/syllabic or completely made-up based on English. One thing these characters are not, they are NOT the "reformed egyptian" (demotic script) of the Rosetta Stone, which is actually a pretty compact form of writing about equal in size to Greek.   As it turns out, Greek and Latin are pretty compact thanks to their declensions and lack of prepositions.  Consider, "Veni Vidi Vici" (I came, I saw, I conquered) or http://www.perseus.tufts.edu/hopper/morph?l=mh%3Dnin&la=greek&can=mh%3Dnin0 http://www.perseus.tufts.edu/hopper/morph?l=a)%2Feide&la=greek&can=a)%2Feide0&prior=mh%3Dnin http://www.perseus.tufts.edu/hopper/morph?l=qea%5C&la=greek&can=qea%5C0&prior=a)%2Feide http://www.perseus.tufts.edu/hopper/morph?l=*phlhi%2Ba%2Fdew&la=greek&can=*phlhi%2Ba%2Fdew0&prior=qea%5C http://www.perseus.tufts.edu/hopper/morph?l=*)axilh%3Dos&la=greek&can=*)axilh%3Dos0&prior=*phlhi+a%2Fdew As to the question of whether any other such "metal book" like to the BoM has ever been found, the answer is yes and no.   Yes, other individual, short-text metal plates and scrolls have been found in the OLD WORLD, but none in the New World that I am aware of.   These Old World assemblages of plates are usually not bound together and contain very few characters per plate.   The Qumran copper scroll is one example.  It seems to be a sort of treasure map and its authenticity is still debated.  The Etruscan "book" cited by other answerers only has SIX total plates, with writing on ONE SIDE of each plate and only about 50 odd characters per plate.   Your average restaurant menu contains more information than this purported "book". Sadly for the Mormons, I do know of one other example of bound, engraved metal plates that were found in the New World -- the infamous brass Kinderhook Plates, uncovered in 1843 in Illinois and taken to Nauvoo where they were put on display and Joseph Smith attempted to decipher them.  Here is their description, according to the Prophet's secretary, William Clayton, "I have seen 6 brass plates...covered with ancient characters of language  containing from 30 to 40 on each side of the plates. Prest J. [Joseph  Smith] has translated a portion and says they contain the history of the  person with whom they were found and he was a descendant of http://en.wikipedia.org/wiki/Ham_%28son_of_Noah%29 through the loins of Pharaoh king of Egypt, and that he received his kingdom from the ruler of heaven and earth." Unfortunately, the Kinderhook Plates were a forgery.   Even though the hoaxers admitted their scam in the 1870's, many in the LDS Church (including General Authorities) still continued to believe in the Kinderhook Plates authenticity as late as the 1970's.   In that decade, forensic tests finally proved the Kinderhook plates were of modern origin and all references to them in LDS publications and circles quickly ceased.   Few younger Mormons have heard of them today and the older ones who remember them don't like to talk about it. After all of the above deconstructive criticism, let me state that I think the "golden" plates actually existed -- and may still exist.   I think that due to unrelenting pressure from his early investor/followers to show them something tangible, Joseph crafted a set of plates out of brass and scratched the characters on himself.   I think that the majority of these brass plates were sealed because Joseph realized what a laborious process it was to etch plates with tiny characters, so he quit as soon as he thought he had enough, and sealed the rest completely so that know one could see they were blank.  These plates didn't have to be perfect, they didn't have to pass rigorous forensic scrutiny.   They just had to wow a few friendly farmer followers for a few minutes, and then they went back in the bag.  The reason they weighed about what a block of brass of those dimensions would weigh is because they were made of brass.   The reason these "1500 year old" brass plates were not tarnished is because they were not of ancient origin.  So where are the plates today?   One school of thought has them in the LDS church's vaults in SLC.   I think not.   I think Joseph probably got rid of them somewhere near his lodgings after their last purported showing and before the date when he said the Angel Moroni fetched them back.   Keeping them around would do him nothing but harm.   I think a good, patient detective armed with a powerful metal detector might be wise to search those environs where Joseph lived before the Angel Moroni showed up to reclaim them.   But that detective should set his detector to brass/copper, not gold, if he goes east in search of this ancient treasure.