Thursday, October 22, 2009
The tiny fēn is about 3 mm. The cùn is traditionally the width of a person's thumb at the knuckle. The chǐ (or Chinese 'foot') is derived from the length of a human forearm, like a cubit. Or so says Wikipedia.
Those were hard-working people, to have thumbs as wide as a cùn.
The ruler is wooden, with brass inlays marking the units.