Both Leonardo and Gregorio Dati are attributed authorship of La Sfera ("The Sphere"), an astronomical-geographic poemetto in ottave, written in the second half of the 14th century, and a work much popular in its time.

This work in verse gives information about the world, the marinaresche compass and other things, adding observations, notes about travel and designs.

In some manuscripts of La Sfera there are designs representing ports, headlands, islands, linked by many lines.

The earlier sermon touched off an exchange of polemical memoranda between Dati and supporters of conciliar supremacy.

Dati's discussion of circumcision was traditional for his time, describing the Jewish rite as superseded by baptism.