be punished according to law. No doubt the punishment of burning was meant; the bull in fact expressly condemns the proposition of Luther which denounces the burning of heretics. All this was called then at Rome, and has been called even latterly by the papal party, "the tone rather of fatherly sorrow than of penal severity." The emperor Charles V, before leaving the Netherlands on his journey to Aix-la-Chapelle to be crowned (1520),[27] had already been induced to take his first step against Luther. He had consented to the execution of the sentence in the bull condemning Luther's works to be burned, and had issued orders to that effect throughout the Netherlands. They were burned in public at Louvain, Cologne, and Mainz. At Cologne this was done while he was staying there. It was in this town that the two legates approached the elector Frederick with the demand to have the same done in his territory, and to execute due punishment on the heretic himself, or at least to keep him close prisoner or to deliver him over to the Pope. Frederick, however, refused, saying that Luther must first be heard by impartial judges. Erasmus also, who was then staying at Cologne, expressed himself to the same effect, in an opinion obtained from him by Frederick through Spalatin. At an interview with the Elector he said to him: "Luther has committed two great faults: he has touched the Pope on his crown and the monks on their bellies." The burning of Luther's books at Mainz was effected without hinderance, and the legates in triumph proceeded to carry out their mission elsewhere.