Former money changer Michael IV the Paphlagonian (1034–41) assumed the throne of Byzantium in 1034 and began the slow process of debasing both the "tetarteron nomisma" and the "histamenon nomisma". The debasement was gradual at first, but then accelerated rapidly: about 21 carats (87.5% pure) during the reign of Constantine IX (1042–1055), 18 carats (75%) under Constantine X (1059–1067), 16 carats (66.7%) under Romanus IV (1068–1071), 14 carats (58%) under Michael VII (1071–1078), 8 carats (33%) under Nicephorus III (1078–1081) and 0 to 8 carats during the first eleven years of the reign of Alexius I (1081–1118). Alexius reformed the coinage in 1092 and eliminated the solidus ("histamenon nomisma") altogether. In its place he introduced a new gold coin called the "hyperpyron nomisma" at about 20.5k fine (85%). The weight, dimensions and purity of the "hyperpyron nomisma" remained stable until the fall of Constantinople to the Crusaders in 1204. After that time the exiled Empire of Nicea continued to strike a debased "hyperpyron nomisma". Michael VIII recaptured Constantinople in 1261, and the Byzantine Empire continued to strike the debased "hyperpyron nomisma" until the joint reign of John V and John VI (1347–1354). After that time the "hyperpyron nomisma" continued as a unit of account, but it was no longer struck in gold.