This section is from the "A Complete Dictionary of Dry Goods" book, by George S. Cole. Also available from Amazon: A complete dictionary of dry goods and history of silk, cotton, linen, wool and other fibrous substances,: Including a full explanation of the modern processes ... together with various useful tables.
Hank. A skein or coil of yarn or thread. More particularly a definite length of yarn, of cotton, linen, silk or wool. A hank of cotton is 840 yards. A hank of linen is 3,000 yards. Silk is not coiled and numbered on the principle of cotton and linen. The fineness of silk yarn is determined by constant length with variable weight, whereas, other yarns are indicated by constant weight with variable length. The original standard length of silk was 12,467 yards, six inches, the numbers being the weight in deniers of twenty-six grains. The number is ascertained by the weight of 12,467 yards and six inches, in grains - 1-24 of a denier of a hank containing 520 yards, twenty inches. Spun silk is numbered on a different principle. It is determined by the cotton standard, the number of skeins of 840 yards each to the pound, making a hank. Woolen and worsted yarns are also numbered in the same manner.