Based on his own visions, these works brought Postel into conflict with the Inquisition. Postel's ties, however, with the very men tasked with trying him led to a verdict of insanity, rather than heresy, which could to the death penalty, and consequently Postel was confined to the Papal prisons in Rome. He was released when the prison was opened upon the death of Paul IV in 1559. Czech humanist Šimon Proxenus ze Sudetu (1532–1575), reports that in 1564 Postel was detained to the monastery of St. Martin des Champs in Paris, "because of his delusions on the Mother Jeanne".