Below is a proposal for a 12 day intensive Prāṇāyāma Sādhana.
Here, the Vinyāsa Krama is built around a single Prāṇāyāma technique, namely Nāḍī Śodhana. The proposal is relatively straight forward in that the practitioner sets a developmentally ascending Krama for the first six days. This is followed by a similarly shaped descending Krama for the remaining six days.
Along with the single Prāṇāyāma technique Nāḍī Śodhana, a single ratio is proposed, namely 184.108.40.206, coupled with the same breath length. In other words starting with and maintaining throughout the sitting the same breath length and ratio, with the exhale twice the length of the inhale.
Here, in terms of Bhāvana, the aim is to cultivate a quality of subtlety or Sūkṣma. This is further facilitated as a process by choosing to maintain a lower breath length, as in 4 or 5 breaths per minute rather than say, 2 or 3 breaths per minute. This would translate as 220.127.116.11. or 18.104.22.168. rather than say 22.214.171.124. 126.96.36.199. or 10.0.20.0.
Thus, the experience is around refining the quality of the flow rather than the length of the flow. Here, I am reminded of my experiences around brushing my daughters long hair, in that it was more about the delicacy and deftness of the movement that untangled the knots, rather than the length and strength of the movement. Though here, I had constant in-house feedback guiding my efforts!
As to time of the day, there are pros and cons, as also whether it sits as a stand alone practice, or is integrated within other aspects of Yoga practice such as Āsana, Mudrā, Dhyāna or Adhyayanam. Within these considerations, one suggestion I would offer is around the effort to maintain a consistency of time and place throughout the twelve days.
Finally, what is the proposal in terms of overall number of breaths in each sitting, and in the ascent and descent of the steps involved? The starting proposal is maintaining Nāḍī Śodhana for 48 breaths or four counting rounds of 12 breaths each as illustrated below.
This increases by adding a further full counting round each day until we reach 108 breaths or 9 rounds. Having remained there for two days, we begin the descent, returning to the starting point via the same Krama as the ascent.
In other words:
Day 1 – 48 Breaths
Day 2 – 60 Breaths
Day 3 – 72 Breaths
Day 4 – 84 Breaths
Day 5 – 96 Breaths
Day 6 – 108 Breaths
Day 7 – 108 Breaths
Day 8 – 96 Breaths
Day 9 – 84 Breaths
Day 10 – 72 Breaths
Day 11 – 60 Breaths
Day 12 – 48 Breaths