An architect redecorated our office. He often uses his body as measurement: his hand is 10 cm wide. His thumb and forefinger 20 cm apart. His forearm is 30 cm long. His foot, too (with his shoe on). His forearm with ring finger is 45 cm long. His arms bridge 180 cm. His eyes are at a height of 1,75 m. Forgot your metering rule? So what.
Source: Wall Street Journal, 2011–01–28, page 11.
You can use man as measure. But only completely. But only artful. As above.
By the way, I am knee-high.