The earth is placed in the central region of the cosmos, standing fast in the center, equidistant from all other parts of the sky . . . . It is divided into three parts, one of which is called Asia, the second Europe, the third Africa . . . . Apart from these three parts of the world there exists a fourth part, beyond the ocean, which is unknown to us.--Isidore of Seville, Etymologies (circa A.D. 600)
