Introduction
Measuring units in folklore and history
Nearly all early units of size were based on the always-handy human body. In the Middle Ages, the inch is reputed to have been the length of a medieval king's first thumb joint. The yard was once defined as the distance between English king Henry I's nose and the tip of his outstretched middle finger. The origin of the foot as a unit of measurement is obvious.
Eventually, ancient "rules of thumb" gave way to more carefully defined units. The metric system was adopted in France in 1799.
