The pseudonym adopted by the author of a medieval treatise on arts and crafts entitled De diversis artibus (The Various Arts). Estimates of the date of composition range from the 9th to the 13th century. C. R. Dodwell, who produced the standard edition of the text, with English translation (1961), assigns it to the period 1110–40. It is the most important source of information on medieval artistic techniques and is unusual for its time in its references to the artist's attitude to his work. Various early manuscripts are extant, but the treatise did not become generally known until the late 18th century. G. E. Lessing produced the first printed edition, posthumously published in 1781, and an English edition, made from another manuscript, appeared in the same year. Little or nothing is known with certainty about the writer, who adopted a pseudonym because he wanted to dedicate his skills to God rather than win fame for himself. However, internal evidence suggests that he was a German Benedictine monk and also a practising craftsman whose primary interest lay in metalwork. He has been plausibly identified with Roger of Helmarshausen, a goldsmith and monk at the abbey of Helmarshausen, near Kassel, who is documented as the maker of a portable altar (1100, Paderborn Cathedral Treasury) for Bishop Henry of Werl. Other works have been attributed to him.