Mikołaj Kopernik, De revolutionibus libri sex, Biblioteka Jagiellońska, BJ Rkp. 10000 III.
Manuscrit autographe

fol 75. Liber III, Caput IV. Quomodo motus reciprocus sive librationis ex circularibus constet
BOOK III CH. 4 HOW AN OSCILLATING MOTION OR MOTION IN LIBRATION IS CONSTRUCTED OUT OF CIRCULAR MOTIONS
Now I shall hereafter show that this motion is in agreement with the phenomena ... ... Therefore it is clear that from two circular motions acting conjointly in this way, a rectilinear motion is compounded, as well as an oscillating and nonuniform motion from uniform motions.
Note rayée : Il est à noter ici en passant, que si les cercles sont inégaux, ils décriront une section cylindrique, nommée Ellipse par les mathématiciens.
It should be noted here in passing that if the circles are unequal, they will describe a cylindric section, called an “ellipse” by the mathematicians.

Note rayée :
Il est à noter ici en passant, que si les cercles sont inégaux, ils décriront une section cylindrique, nommée Ellipse par les mathématiciens.



In the autograph, fol. 75 r , Chapter 4 originally ended with the following passage, which Copernicus subsequently deleted:
It should be noted here in passing that if the circles are unequal, with all the other conditions remaining the same, they will describe, not a straight line, but a conic or cylindric section, called an “ellipse” by the mathematicians.

NICOLAUS COPERNICUS OF TORUN
ON THE REVOLUTIONS OF THE HEAVENLY SPHERES
Translated by CHARLES GLEN WALLIS
Annapolis, St. John's Bookstore, 1939.