In 1794 a Portuguese slave ship, with 512 Mozambican slaves destined for cotton and rice plantations in Brazil, sank off the shores of the Cape of Good Hope, then a Dutch colony. The São José left Lisbon in April 1794, bound for Mozambique via the Cape of Good Hope, with 1,400 iron ballast bars in its cargo. It is believed that most of these were used to pay for slaves from Mozambique, but many remained on board to offset the relatively light weight of the ‘human cargo’ on the ship. On the voyage to Brazil, the captain intended to stop at the Cape for provisions and to sell a number of slaves. When the ship sank, more than 200 slaves died and the survivors were sold into slavery in Cape Town.

The ballast bars from the wreck were discovered in 2011 – each bar weighed 39kg. These artefacts are evidence of the first known slave ship to sink with Africans on board and represent the 400-years of slave trade in which thousands of enslaved Africans died at sea.They are currently on ten-year loan to the Smithsonian’s National Museum of African American History and Culture.

Sixy years previously, Clara the Dutch rhino, had sailed past the same coast from Goa, bound beneath the deck of the ship. The sea routes travelled by Indian rhinoceroses to Europe trace the same lines that slave ships travelled: between Lisbon and European ports, the west and east coast of Africa and the East Indies.