I recently bought a T-shirt with the Eye of Horus on it. I
really just liked the way it looked, but since I knew people
would ask what it meant, I poked around on the internet to find
out. I was surprised and pleased to discover that, in addition
to its significance as a symbol of protection, it also had
significance in commerce. Specifically, it was a fractional
counting system. The eye consists of six pieces, each
corresponding to a power of one-half: 1/2, 1/4, 1/8, 1/16, 1/32,
and 1/64. All the pieces together add up to 63/64, which the
Egyptians rounded up to 1. By drawing different combinations of
eye-pieces, the Egyptians could represent various fractions
(e.g., use the 1/2 and 1/8 pieces to get 5/8). These fractions
were used to measure quantities of land, grain, medicine, etc.
What fascinates me about this is that it was a naturally
occurring use of binary, as opposed to decimal, counting. And
the Egyptians are not alone in having used such a binary system.
The phrase “two bits” for one-quarter of a d