Al-Masudi writes the Murūj al-Dhahab (Meadows of Gold and Mines of Gems) after decades of travel through Iraq, Syria, Palestine, Egypt, Arabia, Persia, Afghanistan, and the western coast of India. It is the first large-scale work to integrate universal history with scientific geography: it precisely describes the monsoon winds of the Indian Ocean, inland seas, East African fauna, and the customs of peoples outside Islam. He introduces the methodological principle of eyewitness testimony as a criterion of authority over written sources. Ibn Khaldun describes him as the imam of historians. The surviving version (947) is a draft of the revised 956 edition, now lost. He wrote 36 works, of which only two survive.