I.the testing or assaying of gold by fire in a cupel (class.).
I. Lit.: “auri experimentum ignis est: id ipsum obrussam vocant,” Plin. 33, 3, 19, § 59: “aurum ad obrussam,” refined, pure gold, Suet. Ner. 44.—
II. Trop., a test, touchstone, proof: “adhibenda tamquam obrussa ratio,” Cic. Brut. 74, 258: “sic verus ille animus probatur: haec ejus obrussa est,” this is its touchstone, its test, Sen. Ep. 13, 1: “si omnia argumenta ad obrussam coeperimus exigere,” to put to the proof, test accurately, id. Q. N. 4, 5, 1.
