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

The use of these stones may have been similar to the use of Go-pebbles. In Go you put the pebbles on the crossings but you could as well put them in between the lines to lay them out in an order. The pebbles here are movable with the mouse and you can try to lay out numbers by yourself. There are several possibilities to do this.