Almagest: Göğün Küresel Olarak Devindiği Üzerine

The general would be such, having taken beforehand that the heaven is spherical and is carried spherically, and that the earth is itself spherical in shape to the senses, as taken in all its parts, as we taught above, along with the seas and the mountains. Since these make minimal elevations in relation to the magnitude of the whole earth, or even the mentioned parts, just as if an earth sphere were constructed from some material, having a diameter of a foot, and a piece of sand were fastened to it, or some minimal hollow of this sort were made bare, the spherical shape would not be altered in relation to the sense; so too, on the earth, in relation to the comparison of its magnitude, the mountains and the hollows in it, being minimal, will not cause an alteration of its shape in relation to the sense of the spherical. By making an examination of the magnitudes of the earth and the greatest mountain, we will prove this same thing next, in the chapter concerning this. Therefore, he assumes it to be spherical, as it is understood to be such from the phenomena surrounding it.