Before revision: It was later perfected by Canova.Putman, Brenda, ‘’The Sculptor’s Way: A Guide to Modelling and Sculpture’’, Stone and Marble Carving by Robert A. Baillie, Farrar & Rinehart, Inc, New York, 1939, p. 305
After revision: However, similar devices were used in ancient times, when the copying of Greek sculptures for the Roman market was a large industry.It was later perfected by Canova.Putman, Brenda, ‘’The Sculptor’s Way: A Guide to Modelling and Sculpture’’, Stone and Marble Carving by Robert A. Baillie, Farrar & Rinehart, Inc, New York, 1939, p. 305