My understanding is that this is not available anywhere else on the net at the moment and I have found it a great overview of anapanasati. Enjoy.
4.2 The First Tetrad
The instructions for the 16 steps of practice in the Ānāpānasati-sutta and its parallels are preceded by an indication that the meditator should retire to a secluded spot to sit down for actual meditation practice. This indication is noteworthy insofar as it gives the impression that, in early Buddhist thought, mindfulness of breathing was considered a form of meditation best cultivated in a setting free from outer disturbances, instead of being a practice one undertakes alongside everyday activities. There does in fact not seem to be an explicit reference in the early discourses to undertaking mindfulness of breathing while one is engaged in some form of activity, such as having a conversation, going somewhere, doing some kind of manual work, etc. Even in the case of descriptions of walking meditation, the instructions are to keep the mind free from defilements, not to watch the breath while one is walking.
Of course, it will always be beneficial to keep the breath in mind, in whatever situation one may be in. Nevertheless, a problem can arise at least for some practitioners when trying to maintain mindfulness of breathing while, at the same time, having to engage in various daily activities and conversations. The fact that the breath is a relatively subtle object naturally requires some degree of mental focus, in order to be kept in mind. The stronger one’s mind focuses on anything, however, the less it will be able to attend to a range of other things that may be happening at the same time. At least in situations where one is actively engaged in a particular task, it can at times be preferable to use a less subtle object to sustain continuity of mindfulness.
An alternative to the breath would be, for example, mindfulness of the whole body. The entire body is a comparatively less subtle and more easily discerned support for mindfulness, making it less of a challenge to be kept in mind while engaging in various activities. The actual instructions in the Ānāpānasati-sutta for being aware of the breath, once one has sat down in a secluded place, begin by directing mindfulness to the phenomenon of the breath as such, reading: “Mindful one breathes in, mindful one breathes out” (MN III 82; translated in Ñāṇamoli 1995, p. 943). The basic distinction between inhalation and exhalation introduced in this way sets a pattern that continues throughout the entire scheme of practice. The distinction between the breath that comes in and the breath that moves out inculcates a continuous awareness of the impermanent nature of the breath, which keeps changing all the time.
This already points to the insight potential inherent in mindfulness of breathing, something that becomes particularly prominent with the last tetrad in the 16-step progression. Before coming to that, however, I first survey the preceding tetrads. The instructions for the first tetrad direct mindfulness to the following aspects while being aware of breathing in and out:
1. Know breaths to be long
2. Know breaths to be short
3. Experience the whole body
4. Calm the bodily formation
In practical terms, this means that, after having become mindful of the breath moving in and out, the meditator next becomes aware of the length of these breaths. These could be either long or short. Here, it is noteworthy that in the Pāli version, the instructions for steps (1) and (2) are worded as alternatives, evident in the use of the disjunctive particle vā, which means “or.” In other words, the point at stake is not that one should be having first long breaths and then short breaths, but rather that one is aware of either long or short breaths.
A distinct characteristic of the early Buddhist approach to meditation on the breath is in fact an emphasis on mere observation, instead of attempting to control the breath in the way this would be the case for someone engaging in a type of practice that involves an intentional controlling of the breathing process. Elsewhere, the early discourses report that, during the period of his quest for awakening, the Buddha-to-be did engage in breath control, yet he found that this did not lead him to liberation (MN I 243; translated in Ñāṇamoli 1995, p. 337 f.).
In principle, the breath is an aspect of the body that happens naturally, but which can also be influenced through one’s intentions. Breathing happens even when no attention is being paid to it, yet one can freely decide to take a deep and long breath, for example. Instead of attempting to control the breath, however, implementing the instructions in the Ānāpānasati-sutta would simply require being aware of the length of the breath as it naturally occurs in the present moment. This length should then be distinguished into two types: belonging to either the category of long breaths or the category of short breaths.
The next step then requires experiencing the whole body. Here, the instructions in the Ānāpānasati-sutta show a shift of terminology, as the discourse proceeds from referring to an act of “knowing,” employed for the first two steps, to using the expression “training,” a term used throughout the remainder of the 16 steps. In the Ānāpānasati-sutta, then, with step (3) concerned with experiencing the whole body, a form of training begins, one trains oneself to experience the whole body while breathing in or breathing out.
The parallel versions differ, as the Saṃyukta-āgama speaks of “training” in the case of each of the 16 steps (T II 206a), including the first two, whereas the three Vinayas do not mention the need for any “training” at all (T XXII 254c, T XXIV 32c, and T XXIII 8a). The notion of engaging in a form of training in relation to mindfulness of breathing, even though this clearly does not imply an attempt to control or even suppress the breath, does point to some degree of intentional monitoring of a natural process that for the most part unfolds on its own. The impression that actual practice involves some degree of intentional monitoring finds further support in the instructions given for the 16 steps. Had there not been a need for some degree of intentional effort or directing of the mind, there would have been little reason for detailed instructions on how to proceed through the 16 steps. So some extent of “training” is indeed required, inasmuch as the practitioner does incline the mind in such a way that the ensuing step can take place.
Yet, at the same time, such “training” is not a forceful matter that involves a strong degree of control, but is probably best understood as a soft kind of nudging of the mind in the proper direction The proper direction to be taken for this third step requires some degree of discussion, as the Pāli commentarial tradition takes the expression “body” in the instruction “to experience the whole body” as intending the body of the breath (Vism 273; translated in Ñāṇamoli 1956/1991, p. 266). That is, the practitioner should become aware of the full length of the breath, being able to distinguish between its beginning, middle, and final parts.
This interpretation is not entirely straightforward, as awareness of the breath in its full length has already been the task of the preceding steps (1 and 2). Unless one has been aware of the whole breath, from its beginning all the way to its final parts, it would not be possible to know if this breath should be reckoned “long” or “short.” So on the explanation suggested by the Pāli commentarial tradition, the third step would not be introducing something distinctly new to the progression of practice, but would just amount to a repetition, or perhaps better a refinement, of awareness of the whole breath.
Here, the parallel versions in the three Vinayas provide a helpful indication, as they formulate the third step in terms of “pervading the body.” Such pervading would indeed present a distinctly new element for the progression of practice, in that from having become aware of the breath in its entire length, the meditator now moves on to becoming aware of the whole body in the sitting posture. This would be a natural progression when turning attention inward, where the breath as an easily noticeable bodily process would then lead on to noticing other and more subtle bodily sensations occurring elsewhere in the body. On this understanding, the third step in the progression would involve a conscious broadening of the field of awareness from the breath alone to the breath experienced within an awareness of the whole body.
The final step in the first tetrad then requires a calming of the bodily formation. Here, the term formation, saṅkhāra, can be understood to mean in particular the breath itself. In addition, the same term could also be taken to stand for any other bodily activity. On this understanding, the instruction would then entail a relaxing of the body in the sitting posture until it becomes naturally still and stable, as well as a calming of whatever other bodily activity may be going on within the body, to the extent that one is able to calm these down. These two interpretations are mutually supportive insofar as a calming of the breath will naturally lead to an increased general tranquility of the body, and tranquility of the body in turn will enhance the calmness of the breathing process. So it seems safe to conclude that step (4) requires calming the breath and the body.
In sum, then, a way of practically implementing the first tetrad of mindfulness of breathing could proceed from becoming aware of the breath to recognizing its length (in terms of either long or short breath), followed by broadening the field of one’s awareness from the breath to the whole body in the sitting posture and then relaxing breath and body, allowing them to become calm. Chief themes of actual practice would then be a firm establishing of mindfulness on the breath and the body together with a gradual calming of both.