“The choice of a proper ratio involves two things,
what can be done and what should be done.
What can be done involves a given person’s capacity
to inhale, hold the breath, exhale and hold the breath.
What should be done involves
our direction of movement, our aim, our need.”
– TKV Desikachar ‘Choosing a Ratio and the proper technique for Prāṇāyāma’
Religiousness in Yoga Chapter Twelve Page 163