Polish priests began instituting reforms influenced by Calvin starting in the 1550s. In 1556 a diet at Piotrków officially instituted several Protestant reforms. Jan Łaski returned to Poland and unsuccessfully attempted to unite the Reformed with the Polish Brethren and Lutherans. In 1575 King Stephen Báthory abandoned Protestantism, leading to the virtual extinction of the Polish Reformed Church. In Bohemia, Reformed ideas began to influence the Unity of the Brethren from the 1540s through Czech students at German and Swiss universities. Emperor Maximilian II tolerated Lutheran and Reformed worship in Bohemia through 1600, and many Bohemian nobles established Reformed worship on their estates. The influence of Calvinism in Swiss and German schools also affected Hungary and Transylvania, with the establishment of the Reformed Church of Hungary in 1576.