Paṭisambhidāmagga Ānāpānasati-Kathā: The Explanation of Mindfulness of Breathing in The Path of Discrimination
56 pages
These are the over two hundred kinds of knowledge that arise in one who develops concentration by mindfulness of breathing with sixteen grounds
… the earliest extant, detailed commentary on Buddhist meditation available in an Indic language
The Path of Discrimination was a key influence on later meditation manuals (such as the medieval Visuddhimagga) and is the oldest such commentary in existence, giving us a rare insight into the early Indian commentarial and meditation traditions.
For a translation of the entire Paṭisambhidāmagga, see SuttaCentral