Peurbach (1474) 9R

ON MERCURY
Mercury has five orbs and an epicycle, the two outermost of which are complementary eccentrics. For the convex surface of the outermost, and the concave surface of the innermost, are concentric with [the center of] the world, but the concave [surface] of the outermost and the convex surface of the innermost [are] eccentric to [the center of] the world. However, they are concentric to each other, and their center is the same distance from the center of the equant as the center of the equant is from the center of the world. And this point is the center of a small circle that the center of the deferent describes, as will be seen. Hence they are called ‘the orbs carrying the auxes of the equant’, and they move around the axis of the Zodiac with the motion of the eighth sphere. Between the outermost and the innermost orbs are two others of similarly variable thickness, holding between them the fifth orb, namely the orb carrying the epicycle. The convex surface of the outer and the concave surface of the inner have the same center as the small circle. But the concave surface of the outer orb and the convex surface of the inner orb, along with each surface of the fifth orb, have a different, moving center, called the center of the carrying orb. These two orbs are called ‘the orbs carrying the auxes of the eccentric’, and they move uniformly around the center of the small circle, in the opposite direction to the order of the Zodiac signs, with a velocity such that in precisely the time that the Sun’s line of mean motion makes one revolution, these orbs similarly complete one revolution in the opposite direction.
THEORICA OF THE ORBS OF MERCURY