De revolutionibus orbium coelestium
When Rheticus printed his "Narratio prima"—the first published account of the Copernican heliocentric system—in 1540 (Danzig), he sent Gasser a copy. Gasser then undertook a second edition (1541, Basel) with his own introduction, in the form of a letter from Gasser to Georg Vogelin of Konstanz. The second edition (1566, Basel) of "De revolutionibus orbium coelestium" contained the "Narratio Prima" with this introduction by Gasser.