Abhidhammavatara

Abhidhammavatara (Pali, also Abhidhammāvatāra), according to Encyclopædia Britannica is "the earliest effort at systematizing, in the form of a manual, the doctrines dealt with in the Abhidhamma (scholastic) section of the Theravada Buddhist canon. The Abhidhammavatara was written in Pali, apparently in the 5th century, by the poet and scholar Buddhadatta in the region of the Kaveri River, in southern India".