The sutta includes sixteen steps of practice, and groups them into four tetrads, associating them with the four satipatthanas (placings of mindfulness).
According to American scholar monk, Thanissaro Bhikkhu, this sutta contains the most detailed meditation instructions in the Pali Canon.
[1] The Theravada Pali Canon version of the Anapanasati Sutta lists sixteen steps to relax and compose the mind and body.
[note 2] The Ānāpānasati Sutta then describes the monitoring of the breath, and relates this to various experiences and practices.
Following the classification of the four satipatthanas, these experiences and practices are grouped into a list of sixteen objects or steps of instructions, generally broken into four tetrads.
[note 3] These core sixteen steps are one of the most widely taught meditation instructions in the early Buddhist texts.
Next, the sutra explicates how contemplation[15] of the four satipatthanas[note 10] sets in the seven factors of awakening, which bring "clear knowing"[13] and release.
The Ānāpānasmṛti Sūtra, as the text was known to Sanskritic early Buddhist schools in India, exists in several forms.
In addition to being in the Anapanasati Sutta, all four of the aforementioned core instructional tetrads can also be found in the following canonical discourses: The first tetrad identified above (relating to bodily mindfulness) can also be found in the following discourses: The Saṃyukta Āgama contains a section titled Ānāpānasmṛti Saṃyukta (安那般那念相應) which contains various sutras on the theme of anapanasati including the sixteen steps.