Pope Gregory IX. Decretales. Basel, 1494.
A very early compilation of papal decisions by Raymond of Penafort. As early as 1230, Raymond was commissioned by Pope Gregory IX to bring the essential law of the decretals -- papal decisions -- together into a single work. The work was promulgated as church law in 1234.
An example of incunabula (Latin for "things in the cradle"), books printed in the first fifty years of printing.