from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
AVOIR DU POIS, comm. law. The name of a peculiar weight. This kind of weight
is so named in distinction from the Troy weight. One pound avoir du pois
contains 7000 grains Troy; that is, fourteen ounces, eleven pennyweights and
sixteen grains Troy a pound avoir du pois contains sixteen ounces; and an
ounce sixteen drachms. Thirty-two cubic feet of pure spring-water, at the
temperature of fifty-six degrees of Fahrenheit's thermometer, make a ton of
2000 pounds avoir du pois, or two thousand two hundred and forty pounds net
weight. Dane's Abr. c. 211, art. 12, Sec. 6. The avoir du pois ounce is less
than the Troy ounce in the proportion of 72 to 79; though the pound is,
greater. Eneye. Amer. art. Avoir du pois., For the derivation of this
phrase, see Barr. on the Stat. 206. See the Report of Secretary of State of
the United States to the Senate, February 22d, 1821, pp. 44, 72, 76, 79, 81,
87, for a learned exposition of the whole subject.