Definition
In old English law, libra means a pound — both as a unit of weight and as a monetary unit equal to one pound sterling. The term appears most frequently in early legal records, chronicle sources, and Domesday-era documents, where it describes currency, rents, and the standard by which coin was measured and valued.
Three recognized compound forms carry distinct technical meanings:
1. Libra arsa ("pound burned"): A pound of coin tested by melting to assess its purity. Assaying by fire verified that coin metal met the required standard before acceptance as payment.
2. Libra arse et pensate ("pounds burned and weighed"): A formula appearing frequently in Domesday Book to describe rents rendered in tested, purified coin — the most reliable form of payment in the early medieval monetary economy.
3. Libra numerata ("pound counted"): A pound of money counted by tale — that is, by the number of coins rather than by weight or assay. This was the ordinary everyday method, as opposed to the more rigorous burned-and-weighed standard.
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Common Language
Modern common usage (Wiktionary): A constellation of the zodiac, traditionally figured as a set of weighing scales; also the astrological sign covering late September through late October.
Historical common usage (Webster's 1913): "The Balance; the seventh sign in the zodiac, which the sun enters at the autumnal equinox in September."
The common meaning and the legal meaning share a common ancestor — the Latin word for scales or balance — but diverged completely in application. In law, libra was never about astrology or the night sky; it referred to the pound as a unit of weight and money, which itself derived from the use of a scale (balance) to weigh coin. Researchers encountering libra in legal records should set aside any astronomical association entirely.
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Common Confusion
The three compound forms — libra arsa, libra arse et pensate, and libra numerata — are easily confused with one another and with the plain term libra when transcribing or reading medieval records. The distinction matters: a rent recorded as "libra numerata" was paid in counted coin, which might be debased; a rent recorded as "libra arsa" or "libra arse et pensate" was paid in tested, purer coin and represented a higher standard of obligation. Treating these as interchangeable misreads the economic significance of the original document.
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Why It Matters in Research
Researchers working in medieval English legal history, early property records, or Domesday scholarship will encounter libra primarily in three contexts: monetary valuation of land and rents, records of payment obligations, and assay standards for coin.
The critical navigational point is that libra in legal sources is not simply "pound" in the modern sense. The distinction between libra numerata (counted) and libra arsa (burned/assayed) reflects a real and historically significant difference in how obligations were discharged and how coin quality was monitored. Medieval landlords and the Crown often specified the assayed standard precisely because clipped or debased coin in counted quantities would not meet the same value as purified coin.
The term falls out of active legal use after the medieval period. It does not appear as a living term in early modern or modern legal dictionaries in its own right. Researchers should therefore treat libra as a term anchored to pre-modern English records, with Domesday Book, early pipe rolls, and related sources being the primary contexts in which it operates.
Cross-referencing to the entry for POUND is essential, as many legal dictionaries treat libra as a direct Latin equivalent and discuss the monetary history under that heading rather than here.
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Historical Dictionary Support
The historical dictionaries are in close agreement on the core definition. Black's (1st Ed.), Black's (2nd Ed.), Rapalje & Lawrence, and Burrill all define libra as a pound — both weight and money — and all situate it in old English law without controversy.
Black's 2nd Ed. provides the most granular treatment, breaking out libra arsa, libra arse et pensate, and libra numerata as distinct sub-entries and citing Spelman and Cowell as authorities. Burrill adds the Fleta citation, which is genuinely instructive: "Viginti denarii faciunt unciam, et duodecim unciae faciunt libram" — twenty pennies make an ounce, and twelve ounces make a pound, both in weight and in number. This makes explicit that the pound as a monetary unit was originally calibrated against the pound as a unit of weight, giving libra its dual character.
Rapalje & Lawrence contains what appears to be a printing artifact or manuscript concatenation error in the available text: the libra entry bleeds into an unrelated passage on licenses and leases. Researchers should be aware that this source's treatment of libra is incomplete and should be supplemented by Black's 2nd Ed. and Burrill.
None of the historical dictionaries provide extended discussion of the assay process itself or the monetary policy significance of the libra arsa standard; researchers needing that context will need to consult numismatic and economic history sources beyond the law dictionary shelf.
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Jurisdictional Note
Libra as a technical legal term is specific to the English common law tradition and its medieval documentary record. It does not carry operative legal meaning in modern common law or civil law jurisdictions. Continental civil law systems used the term in related but distinct monetary and weight contexts, and researchers working in comparative medieval law should not assume English and Continental usage were identical.
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