John of Roquetaillade (de Rupescissa), Franciscan alchemist, date of birth unknown; d. probably at Avignon, 1362. After pursuing the study of philosophy for five years at Toulouse, he entered the Franciscan monastery at Orléans, where he continued his studies for five years longer. His experiments in distillation led to the discovery of what he termed aqua vite, or usually quinta essentia, and commended as a panacea for all disease. His work as an alchemist forms the subject-matter of “ De consideratione quintæ essentia” (Basle, 1561) and “De extractione quintæ essentia”; likewise “Libellus de conficiendo vero lapide philosophico ad sublevandam inopiam papæ et cleri in tempore tribulationis” (Strasburg, 1659). His false prophecies and violent denunciation of ecclesiastical abuses brought him into disfavour with his superiors, resulting in his imprisonment by Clement VI (1345) and Innocent VI (1356). While there he wrote in 1349 his “ Visiones seu revelationes”, and in 1356 “Vade Mecum in tribulatione” and “ Ostensor” a Brown, “Fascicula rerum expetendarum et fugiendarum”, III, London, 1640). His other works include commentaries on the Sentences and on the “ Oraculum pelt ”, “Fragmenta revelationum”, “ Apologus propheticus”, “ De famulatu philosphiæ ad theologiam”. SBARALEA, Suppl. ad script. Ord. Min. (Rome, 1806); JEILER in Kirchenlex., s. v. Johannes von Roquetaillade; SCHNÜRER in Kirchliches Handlex.
F. M. Rudge.