In Teutonic countries the usual system of dividing the pounds was as follows:
Mint-marc of 8 oz. × 20 dwt. × 24 grs. (or 32 azen). Oz. of 480 grains. Medicinal lb. of 12 oz. × 24 scruples × 20 grs. Oz. of 480 grains. Commercial ⎧ Marc of 16 loth × 16 ort (German). ⎩ lb. of 16 oz. × 16 drams (English).
The Latin nations followed the ancient Roman system of dividing the ounce:
Mint-pound of 12 oz. × 6 sextulæ × 24 siliquæ = 1728 siliquæ, the ounce being of 6 × 24 = 144 siliquæ or carats, and the carat of 4 grains, giving 576 grains in an ounce.
Medicinal lb. of 12 oz. ⎧ × 8 drachmæ × 3 scrupuli × 24 granæ, ⎩ × 8 drachmæ × 3 scrupuli × 2 oboli × 12 granæ.
Pound of 16 oz. × 8 ternau × 3 denié × 24 gran.
There we see the scruple becomes a pennyweight, and the obolus or half-scruple becomes a halfpenny.
Mint-marc 8 oz. × 8 gros × 3 deniers × 24 grains. Medicinal lb. of 12 oz. × 8 drachmes × 3 scrupules × 24 grains. Commercial lb. of 16 oz. × 8 gros × 72 grains.
In this system, common to France, Spain, Portugal, Florence, and Rome, the ounce is divided into 576 parts or grains, while the Troy ounce of the rest of Europe is of 480 grains. This makes the Latin grain lighter.
In the medicinal pound, more or less international throughout the West, the 24 Scruples of the ounce are grouped into 8 drachms of 3 scruples.
It may be concluded that the English Troy pound was a Northern weight with its ounce of 480 instead of 576 parts. It has no direct connexion but in name with the marc of Troyes. It probably came to us as an apothecary’s and goldsmith’s pound, and in the latter, the Latin factors 24 scruples × 20 grains were transposed for mint purposes so as to preserve the ancient pennyweight 1/20 ounce of the Tower pound. But in the apothecary’s Troy pound the ounce remained divided into 24 scruples (8 drachms of 3 scruples) each of 20 grains as in other countries except France, &c.
The story of the goldsmiths’ Carat and Grain will be found in Chapter XX, that of the Provençal weights, from which the French Troy was derived, in Chapter XVIII.
The myth of the 32 wheat-corns which formed the basis of the Tower pound = 5400 grains, passed to the Troy pound = 5760 grains, and this deliberate fiction lasted till the time of Elizabeth and perhaps later. It did little harm as regards these mint-pounds, but its application to the Averdepois pound, alleged to be an offshoot of the royal pound, either as 25 shillings, that is 300 pennyweights of 32 wheat-corns, or as 15 ounces Troy, or at a later period as 16 ounces Troy, produced a mental obliquity which is most lamentable.