Casimir's official cult started spreading soon after his death. Already in 1501, Pope Alexander VI, citing chapel's splendor and Casimir's miracles, granted a special indulgence to those who would pray in the chapel where Casimir was buried from one vespers to another during certain Catholic festivals, and would contribute to the upkeep of the chapel. In 1513, Andrzej Krzycki wrote a poem mentioning numerous wax votive offerings on Casimir's grave. In 1514, during the Fifth Council of the Lateran, Casimir's brother Sigismund I the Old petitioned the pope to canonize Casimir. After repeated requests, in November 1517, Pope Leo X appointed a three-bishop commission and later sent his legate Zacharias Ferreri to investigate. He arrived at Vilnius in September 1520 and completed his work in about two months. His findings, the first short hagiography of Casimir, was published in 1521 in Kraków as "Vita Beati Casimiri Confessoris". The canonization was all but certain but Pope Leo X died in December 1521. Research of Zenonas Ivinskis and Paulius Rabikauskas showed that there is no documentary proof that he issued a papal bull canonizing Casimir but many important documents were lost during the Sack of Rome (1527). The Protestant Reformation attacked the cult of saints and there were no new canonizations between 1523 and 1588. However, Casimir was included in the first "Roman Martyrology," published in 1583.