Narratio Prima

It is an introduction to Copernicus's major work, De revolutionibus orbium coelestium, published in 1543, largely due to Rheticus's instigation.

[1] Copernicus, born in 1473 and already well over 60 years old, had never published any astronomical work, as his only publication had been his translation of poems of Theophylact Simocatta, printed in 1509 by Johann Haller.

[2] This Narratio Prima, published by Franz Rhode in Danzig in 1540, is still considered to be the best introduction to Copernicus' De revolutionibus orbium coelestium.

As the full[3] title[4] states, the Narratio was published as an open letter to Johannes Schöner of Nuremberg (Nürnberg).

During his two-year stay in Prussia, Rheticus published works of his own, and in cooperation with Copernicus, in 1542 a treatise on trigonometry which was a preview to the second book of De revolutionibus.