Quote Originally Posted by xsnaggle View Post
I think it came from times when people were 'educated' in the modern sense, which is where things like a gross (144) came from (because it was the largest number you could count easily on the fingers of your hands).
I think that the rule of thumb was another measure based on the principle that the average distance from the tip of a person's thumb to the first joint, measured on the top was roughly 1 inch. So small but important things could be measured by it. Similarly the distance from an adult male's finger tip to the tip of his nose was generally regarded as about 1 yard, and in the absence of a ruler or tape it was how drapers measured cloth. I can still remember as a child watching my mother buying net for the curtains and the vendor measuring it like that in the market.
Very interesting, Cheers Snaggs