Yaqut al-Hamawi (1179-1229) was born in Byzantium, sold as a slave to a Syrian merchant, and later educated in Arabic and freed, traveling in Iran, Iraq, Syria, and Egypt. In his Mujam al-Buldan (Dictionary of Countries, 1212) he described merchant caravans traveling from Sijilmasa (in southeastern Morocco) to the kingdom of Ghana and explained how the camels often saved travelers' lives:

On their way they cross desert plains, where the samum (noxious) winds dry up the water inside the water skins. They employ an artful means to carry water in the desert in order to survive. Thus they take with them unloaded camels, which they cause to thirst for one day and one night before they reach the water place, and then they let them drink a first time, and a second until their bellies are quite full. Then the camel drivers...