STONE

British unit of weight equivalent to 14 pounds avoirdupois (6.35 kg). Originally any good-sized rock chosen as a local standard, the stone came to be widely used as a unit of weight in trade, although its value fluctuated with the commodity and region. In the 14th century England's exportation of raw wool to Florence necessitated a fixed standard. In 1389 a royal statute fixed the stone of wool at 14 pounds and the sack of wool at 26 stones. Trade stones of variant weights persist, such as the glass stone of 5 pounds. The stone is now commonly used to designate the weights of people and large animals.