4. Roman Weights and Measures of Capacity

Used by the Greek colonies in Asia, the Greek-Asiatic talent passed to the Greek or Trojan colonies in South Italy, and became the source of the old Roman pound, the As libralis = 5049 grains, 1/100 of the talent; (72·13 × 7000)/100 = 5049 grains.[[8]]

The Aes or As, the bronze or copper pound of the Roman republic in its earlier times, was divided into 12 ounces, each = 420·75 grains.

It remained the mint-pound of both Republic and Empire.

The Aurei of Julius Caesar, 1/40 As, weigh 127 grains, those of Augustus 125 grains. The mean weight appears to be about 126 grains, which gives 5040 grains for the As.

The Aurei of the later Empire were struck at 1/72 As, and weigh 70 grains, giving the same weight, 5040 grains, for the As. At 70·1 grains they would give 5049 grains, the calculated weight of the As.

The evolution of the As from the Greek-Asiatic talent leads to consideration of the measures connected with it, and with the Alexandrian talent.

It has been seen that the Roman foot, 1/5000 of the Roman mile, 8 Olympic stadia, was 11·67 inches. This foot being cubed, the weight of the cubic foot of water was made the basis of the Roman measures of capacity—

11·673 inches = 1589 c.i. = 57·32 lb. water

= 401,240 grains.

This calculated measure, 57·32 lb. = 5·732 gallons = 45·8 pints, was the Amphora Quadrantal, supposed to weigh, of wine, 80 As or primitive pounds. Quadrantal vinei octoginta pondo sit. The correspondence was only approximate. The Quadrantal should have been = 57·7 lb. for its 1/80 part (= 5049 grains) to correspond with the As. Its capacity was probably adjusted so as to make it half a Medimnos and = 3 Modii.

There are specimens extant of the Quadrantal, of cubical shape, showing that it was named from its being a cubic foot in measure.

The Quadrantal, being equal to 45·8 pints, was almost exactly half the Greek Medimnos, equal to 91·5 pints; so that, divided into 8 congii, each of 6 sextarii, the Sextarius, 1/48 Quadrantal, was practically the same as the Xestes, 1/96 of the Medimnos.

And the Quadrantal being also very nearly two-thirds of the Greek Metretes, equal to 70·4 pints, the Sextarius was also nearly the same as the other Xestes, 1/72 of the Metretes.

So the Sextarius was 1/48 Quadrantal, 1/72 Metretes, and 1/96 Medimnos.

The relation of the Roman Modius to the Alexandrian-Greek medimnos appears to be only a coincidence, as the former is one-third of a Roman cubic foot, and the latter an Alexandrian cubic foot increased in water-wheat ratio.

The New Roman Pound

Trade with Egypt led the Romans, not only to use the Alexandrian medimnos, but also to put aside the As for commercial purposes and adopt a standard taken from the Alexandrian talent. Its 1500 double-shekels made 125 libræ each of 12 unciæ = 437 grains. The libra was thus = 5244 grains as compared with the As = 5049 grains.

A further uncial division of the libra made the Uncia either of 6 sextulæ, 24 scrupuli, 48 oboli, 144 siliquæ, or of 12 semi-sextulæ, 144 siliquæ.

The siliqua was a little less than the Eastern qirát, being 3·03 grains instead of the 3·1616 grain carat of the Ptolemaïc series of weights.

Table of Roman Weights and Measures of Capacity

Weights

OLD WEIGHTS (MINT SERIES)

As = 5040 grs.12unciæ
Deunx11„
Dextans10„
Dodrans9„
Bessis8„
Septunx7„
Semissis6„
Quincunx5„
Triens4„
Quadrans3„
Sextans2„
Uncia = 420 grs.1„

NEW WEIGHTS (MEDICINAL SERIES)

Libra=5244 grs.
Uncia=437 „
Sextula=72·8„= 1/6 uncia
Denarius=62·45„= 1/7 uncia
Drachma=54·6„= 1/8 uncia
Scrupulus=18·2„= 1/3 drachma
Obolus=9·1„
Siliqua=3·03„
Chalcus=1 „= 1/3 siliqua
Lens (Sitarion)=3/4„= 1/4 siliqua

Measures

WINE

Metretes (Gr.)= 8·8gall.
Quadrantal80As= 5·77„
Urna40„
Congius10„= 5·77pints
Sextarius20unciæ= 0·96„
Hemina8„
Acetabulum2„
Cyathus1„
Ligula1/4„

CORN

Medimnos=11·45 gall.=2 quadrantal
Modius=1·92 gall.=1/3 quadrantal