As far back as the 10th century, the British government tried to standardize measurements--legend has it that King Edgar declared the measurements used at Winchester, his capital, would be standard throughout the kingdom.
Three hunded years later, the drafters of the Magna Carta threw in a clause providing that "there should be one measure of wine, one of ale and one of corn and it should be of weights as of measures."
It was not until 1585 that a Flemish monk proposed a decimal-based measuring system, a proposal that went nowhere for 85 years until Gabriel Mouton, the vicar of a church in Lyons, France, proposed a system based on the physical universe (a meter's length is an established fraction of the arc of the earth) instead of the human body, according to Frank Ross Jr.'s book "The Metric System--Measures for All Mankind."
Another century passed before the French government, in the person of minister Charles-Maurice Talleyrand, directed the French Academy to study the issue in 1790. The meter was established in 1793, and the metric system was adopted by the French two years later.
Between 1865 and 1955, Germany, China, Japan and many other nations picked up the system; by 1979 Britain, South Africa, Canada and Australia had gone metric.
Use of the metric system has been legal in the United States since 1866.