Arithmetic and Weaving in Antiquity
A pebble proof of the incommensurability in the square

This image from a Greek vase shows Achilles and Ajax playing a board game. They use small stones called psephoi. It is supposed that the Greeks developed the first mathematical proofs with such pebbles by using number features like even, odd, prime or the like.
To weave the pattern that is seen on the warrior's coats a weaver also needs to know about these number features and their divisibility.