Friction ultimately stops both the spin and the wobble of the top, but this influence seems wholly absent in the case of the earth, and both rotation and precession go on unchanged from century to century, save for certain minor forces which for a time change the direction or rate of the Precessional motion, first in one way and then in another, without in the long run producing any results of consequence.
"A Text-Book of Astronomy"
George C. Comstock
There are only two bodies in the universe which sensibly contribute to the Precessional movement of the earth's axis: these bodies are the sun and the moon.
"The Story of the Heavens"
Robert Stawell Ball
The Precessional effect of the sun is to cause this point-the pole of the earth-to revolve, always preserving the same angular distance from the pole of the ecliptic; and thus we have a motion of the type represented in the diagram.
"The Story of the Heavens"
Robert Stawell Ball