Definition:Roman Weights and Measures/Mass/Libra
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Definition
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.
Sources
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $12$
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $12$