One of the most popular pieces of Akan art are the Akan goldweights. The gold weights were made of copper, bronze, and brass. They were cast using a method of casting known as lost-wax technique or "cire perdue". Goldweights were created for economic transactions involving gold. Although it is not clear when the convention of weights were first introduced, scholars suggest that the Akan first traded gold with Muslim merchants from the West African interior, long before European contact. Their weight system correspond to the Islamic weight system of North Africa, and appear to be part of early sub-Saharan trade.