Definition:Roman Weights and Measures/Mass/Libra

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The libra is a unit of mass that was part of the Roman system of weights.

$1$ libra $= 12$ unciae.

Its value in modern units is estimated to be approximately $5 \, 076$ grains or $329$ grams.

Historical Note

The libra has continued to be used throughout history, and evolved into the pound.

Hence the symbol $\text{lb}$ to indicate pound weight.

Linguistic Note

The word libra is a Latin word that literally means balance.

Its plural is librae.

In David Wells: Curious and Interesting Numbers, it is referred to (in passing) as a unit, but this has not been corroborated.