An Arab ship, around 1237, engaged in the East African trade in the Persian Gulf. This is a miniature from the al-Maqamat of al-Hariri, Baghdad. The ship is clearly meant to ply open waters, though it does not show all that clearly the triangular lateen sail that Arab and other ships used, which enabled them to steer against the wind when necessary. Maritime trade on the Indian Ocean changed little from the Bronze Age to the advent of the internal combustion engine.