But the king had a mint-pound of his own, and he had to reconcile the existence of the coinage-pound and of the commercial pound with the customary declaration of unity of weight made in each reign. The king’s councillors evaded the difficulty by pretending that the measures of capacity were based on the mint-pound and, in statutes where a commercial pound had to be mentioned, by pretending that this was equal to 25 shillings weight or 15 ounces of the mint-pound. This deception led to others, so that, to make out the meaning of a statute of weights and measures, one must be able to read between the lines, and to be prepared for misleading and contradictory statements. I will take as an instance, Act 51 Henry III (1267):
An English peny called a Sterling, round and without clipping, shall weigh 32 wheat corns in the midst of the ear; and 20 d. do make an Ounce, and 12 Ounces one Pound, and 8 Pounds do make a gallon of wine and 8 gallons of wine do make a London Bushel which is the eighth part of a Quarter.
This declaration may be thus interpreted:
In the Tower there is a standard pound. An English silver penny should weigh 1/240 of this pound and 1/20 of its ounce, and the penny-weight may be divided into 32 aces or little grains. But there is another old-established pound used for all goods but gold and silver, bread and drugs. Our regard for the unity of weight forbids us to describe this pound otherwise than by mentioning that a wine-gallon contains 8 of these pounds weight of wine or of water, that 8 larger gallons each containing 8 pounds, not of wine, but of wheat, make a Bushel; and that 8 of these bushels make a quarter of a Chaldron containing a ton or 2000 lb. of wheat.
The Bushel is 1/8 of the Quarter, which was the quarter of a chaldron, the measure of a ton of 20 true hundredweight. The quarter was 500 lb. of average wheat, and the bushel weighed 500/8 = 62-1/2 averdepois lb. of wheat or, in wheat-water ratio, 78 lb. of wine or of water, the specific gravity of which differs but little. But 8 × 8 Tower lb. of wine = (5400 grs. × 8 × 8)/7000 = 49·4 averdepois lb. or, to be quite accurate, 49·5 lb. of early Plantagenet averdepois weight, when the ounce was of Roman standard, 437 grains; how then could the bushel = 78 lb. of wine, be the measure of 49·5 lb. of wine?