Proclus: On the Sphere; Cleomedes: On the World; Aratus: Phenomena

I wished to call them synergoi collaborators/coworkers, because they are all occupied with the same work, and they pass it on to each other as if by hand to finish it. For one divides its circumference; another explains the use of that division more fully; the third paints the divided parts from above; the fourth cultivates the same from below. By these, I certainly mean to say this: PROCLUS, indeed, being placed in the first rank, having noted points, lines, and circles—whether by calculation alone—establishes only certain spaces of the heaven and earth, and distinguishes the inhabited from the uninhabited. A material sphaera sphere, as they call it, places an image of this section before our eyes; from which the author himself wished this little book to be named peri sphairas on the sphere.