About the same time, Hanno the Navigator was sent to explore the western coast of Africa. His periplus has survived and is one of the earliest surviving manuscripts. The periplus records landmarks, ports and sailing distance between them. It is a guide for other ship captains to follow. Hanno's 60 ships moved south along the African coast. He may have reached as far as an island off the coast of Sierra Leone. There is no record of any other explorations of the west Africa coast until the time of Henry the Navigator, the Portuguese explorer.