Emily Dickinson Lexicon

TROY, or TROY-WEIGHT, n. [said to have been named from Troyes, in France, where it was first adopted in Europe. The troy ounce is supposed to have been brought from Cairo during the crusades. Some persons however say that the original name was tron.]

The weight by which gold and silver, jewels, medicines, &c. are weighed. In this weight, 20 grains = a scruple, 3 scruples = a dram, 8 drams = an ounce, and 12 ounces = one pound. In weighing gold, silver, &c., scruples and drams are not used, but the pennyweight, which is 24 grains, is employed in their stead; the pennyweight is not used in weighing medicines.