De revolutionibus orbium coelestium
The Commentariolus ("Little Commentary") is Nicolaus Copernicus's brief outline of an early version of his revolutionary heliocentric theory of the universe. After further long development of his theory, Copernicus published the mature version in 1543 in his landmark work, "De revolutionibus orbium coelestium" ("On the Revolutions of the Heavenly Spheres").