The work which gained him greatest reputation was his "De Asse et Partibus Eius" (1514), a treatise on ancient coins and measures. He was held in high esteem by Francis I, who was persuaded by him, and by Jean du Bellay, Bishop of Narbonne, to found the Collegium Trilingue (afterwards the Collège de France) and the library at Fontainebleau, which was removed to Paris and was the origin of the Bibliothèque Nationale. He also induced Francis to refrain from prohibiting printing in France, which had been advised by the Sorbonne in 1533. Earlier, he had been sent by Louis XII to Rome as ambassador to Leo X, and in 1522 was appointed "maître des requêtes" and was several times "prévôt des marchands".