As a young student he easily distinguished himself by the translation of several philosophical, mathematical, and medical books from Arabic or Latin into Hebrew. King Robert of Naples, who was then living in the south of France, hearing of his proficiency, commissioned him to go to Rome and translate some Hebrew books into Latin for him. While Kalonymos was in Rome he was a great favourite with all who knew him intimately, and, owing to his fine appearance, his prominent position, and his manifold accomplishments, he had no difficulty in obtaining entry into the best Roman society. Several of his contemporaries, and more especially Immanuel di Roma, a friend of Dante, speak of him in high terms, and bestow upon him, too, his father's title of _Nasi_. Whilst in Rome Kalonymos was asked by the leaders of the Jewish community of Avignon, where he and his parents had lived for some time, to come thither in order to take a petition to the Pope, who was then residing there, praying that he would exert his influence in favour of the Jewish inhabitants of Avignon, for whose extermination the Christian population had planned a secret plot. It is not known what the result was. Graetz, in his History of the Jews (vol. VII, p. 305), states that Kalonymos died about the year 1337, but he does not mention the place of his death. Kalonymos's chief work is, by general consent, his _Eben Bochan_ (“The Touchstone”), manuscripts of which are to be found in several libraries, including those of Munich, Leyden, Paris, and Florence. Printed as an _editio princeps_ at Naples in 1489, a second edition appeared at Venice in 1558; it was subsequently published at Sulzbach in 1705, and again at Fürth (without a date), and also at Lemberg in 1865. In 1878 Dr. Kayserling edited the late Dr. Meisel's posthumous German translation in verse, to which he added a brief sketch in German of Kalonymos's life and principal works.