Definition
Latin legal term from old English law meaning "a pound burned" — that is, a pound of silver that had been tested for purity by melting or assay. The term describes a standard of monetary payment in which coin was verified by fire rather than merely counted or weighed.
The full phrase libra arsa et pensata (pounds burned and weighed) appears frequently in Domesday Book to denote rents and dues rendered in coin of proven purity, as distinguished from face-value or unchecked currency. The burning test (combustion assay) removed base or debased coin from the reckoning, ensuring the creditor received silver of actual standard.
A related term, libra numerata, denotes the opposite: a pound counted by tale — that is, money accepted by count of coins rather than by weight or assay. The contrast between these two standards is the operative distinction in medieval English fiscal records.
Common Confusion
Libra arsa should not be confused with libra numerata. The two terms describe opposite modes of satisfying a monetary obligation in medieval English practice: libra arsa requires proof of purity by assay; libra numerata requires only that the correct number of coins be tendered. Domesday and exchequer records use both, and misreading one for the other inverts the payment standard being described.
Why It Matters in Research
This term is almost exclusively a Domesday Book and medieval exchequer term. Researchers encountering it will be working in the history of English monetary obligation, feudal tenure, or early fiscal administration — not in any living legal doctrine.
The critical navigational point is that libra arsa describes a payment standard, not a coin or denomination. When Domesday entries specify rent in librae arsae et pensatae, the scribe is recording a quality guarantee attached to the payment, not a separate currency. Researchers conflating it with a monetary unit will misread the underlying obligation.
The contrast with libra numerata is analytically important: Domesday and exchequer records use both standards, and the choice between them can reveal the relative power of lord and tenant in a given transaction, as well as the state of the local coin supply. A rent rendered by tale (numerata) imposed currency risk on the recipient; one rendered by assay (arsa) shifted that risk to the payer.
Because this term appears almost nowhere outside Domesday scholarship, modern legal dictionaries treat it as historical artifact only. Researchers should not expect it in case law or statute. The primary research pathway runs through Spelman's Glossarium Archaiologum and Cowell's Interpreter, both of which are the cited authorities in all three source dictionaries, and through the Domesday Book itself.
Historical Dictionary Support
All three source dictionaries — Black's, Rapalje & Lawrence, and Burrill's — are in close agreement, drawing from the same two authorities: Spelman and Cowell. The definitions are substantively identical: a pound of money tested by melting to verify purity, used in Domesday to specify the quality of rent payments.
Rapalje & Lawrence adds the most useful comparative information by immediately appending the contrasting term libra numerata (a pound counted rather than weighed), making the functional distinction explicit. Black's and Burrill's note the Domesday context most prominently, both describing it as "a frequent expression" in that source.
No source dictionary provides meaningful doctrinal analysis because there is none to provide. This is a term of historical description, not legal rule-making. Researchers relying on any of these entries for substantive legal argument would be misusing them; their utility is strictly definitional and contextual.
Spelman's Glossarium and Cowell's Interpreter, cited by all three dictionaries, remain the authoritative historical sources for this term. Neither is a modern legal authority, but both are accessible and appropriate for medieval English legal history research.