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Comment by kevinwang | Hacker News Reader

Well the linked page says:

It’s also not surprising that they could create a flat surface or angles that are exactly-ish 90 degrees. The Egyptians boast some of the earliest known texts on geometry, like the Rhind Papyrus (from around 1650 BCE) and the Moscow papyrus (from about 1850 BCE). The latter papyrus indicates that the Egyptians could approximate pi (as 3.16049) and find the volume of a truncated pyramid. It stands to reason that 500 years later, they would be able to carve a flat surface and make a corner of exactly-ish 90 degrees.

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I was referring to the precision of the boxes, not Brien Forester's quote about it, and more specifically the surface that is mirror polished to several ten-thousandths of an inch as estimated with a precision straight edge and toolmaker's square by someone who was a precision machinist, engineer, "master craftsman" (member of a professional guild), and a member of Mensa. These tools are so precise that if you drop them on the ground, handle them the wrong way or they end up in untrusted hands, they have to be re-calibrated and verified.

I apologize if this is an order of magnitude beyond most peoples' understanding and experience. It's probably not your occupation, so please don't take it personally. As an example of what this degree of precision is, consider a thin hair which is about four thousandths of an inch in diameter. If you slice that diameter up ten times, you will then have something that is as small as or at least reasonably approaching this measurement.

I see. Very interesting if true.

If you look at marble statues, a square box is hardly amazing in comparison. "a few ten-thousandths of an inch" - close to micro meter precision - sounds almost like exaggeration, but some type of stone might just split in a very planar way.

Yes, there are some amazing marble statues. Have you seen the one where there is a fishing net cut from marble? Or the twins from Russia - two identical statues except for some obvious clumps of hair of hair, as if an image was taken at different times, in the breeze, and an artist or machine reproduced the statue from the image. I am assuming that most marble statues are at least an order of magnitude less precise than the granite box. Granite, by the way, is composed of different materials, such as, for example, feldspar and quartz. It doesn't break along a plane. Yes, a micrometer is .0001". Calipers, on the other hand, often only measure to .001" and would not be able to measure anything this precise.

> "a few ten-thousandths of an inch" - close to micro meter precision - sounds almost like exaggeration, but some type of stone might just split in a very planar way.

Not an exaggeration, just an extremely long time spent hand grinding/polishing with fine grit tools/paste.

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