It is almost impossible to write the history of the eastern African coast without consulting the Periplus of the Erythraean Sea, a travel guide book written by an anonymous eyewitness, believed to be a ship captain or sailor who had visited the coast of eastern Africa around the middle of the first century ce. Written in Greek, the book provides valuable information regarding cultural, social, political, commercial as well as environmental aspects of the region at the time. Regarding metals, for example, the author states: ‘Into these market-towns [of the eastern African coast] are imported the lances made especially for them at Mouza [Muza], hatchets, swords, awls, …’ and from eastern Africa ‘Much ivory is taken away … and also rhinoceros horn and tortoise-shell, … and a little coconut oil’ (Collins 1990: 48–9).