Definition:Roman Weights and Measures/Mass/Calcus
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Definition
The calcus is the smallest unit of mass in the Roman system of weights.
Its value in modern units is estimated to be approximately $2.2$ grains, or approximately $0.14$ grams.
Linguistic Note
The word calcus can be found in David Wells: Curious and Interesting Numbers, in his discussion on the number $12$ (twelve).
This has not been corroborated on the Internet, and it is possible that it is a misprint for calculus, which is Latin for small pebble.
Its plural, on the assumption that it is a second declension noun, which is reasonable, would be calci.
Sources
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $12$
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $12$