Originally based on the weight of grains or leguminous seeds, which, of course, varied in size from place to place, the carat was equivalent to 0.2053 gram (3.168 troy grains) in London, 0.1972 g in Florence, and 0.2057 g in Amsterdam.
The avoirdupois pound, at 7,000 grains, exactly corresponded with the British, as did the troy pound at 5,760 grains; however, the U.S. bushel, at 2,150.42 cubic inches, again deviated from the British.
Ounce, unit of weight in the avoirdupois system, equal to 1/16 pound (437 1/2 grains), and in the troy and apothecaries' systems, equal to 480 grains, or 1/12 pound.
The apothecaries' grain is equal to the troy and avoirdupois grains and represents 1/5,760 part of the troy and apothecaries' pound and 1/7,000 part of the avoirdupois pound.
The traditional English apothecaries' system of weights is as shown in the table, the pound, ounce and grain being identical to the troy pound, ounce and grain.
The English version of the system is closely related with the English troy system of weights, the pound and grain being exactly the same in both.
Troy weight, traditional system of weight in the British Isles based on the grain, pennyweight (24 grains), ounce (20 pennyweights), and pound (12 ounces).
