In stage 1 we merged the mantra Soham with the breath. In stage 2 the mantra Hamso was merged with the breathing process. In stage 3 the mantra was split into separate parts So and Ham which were individually synchronized with respiration. In stage 4, to be described shortly, So and Ham will be merged with the breathing process so that they form a continuous cycle . . . So-Ham-So-Ham-So and so forth. The sound of So should merge with Ham so that there is no break in the cycle. Before So ends, Ham should start and before Ham ends, So should start. If you have done the previous three stages you will find that this fourth stage comes naturally. If you have not done the preparatory stages then you will find stage 4 difficult if not impossible.
The technique of stage 4 is as follows:
Take a comfortable sitting position.
Close your eyes.
Relax the whole body and adjust yourself so that you feel no need to move.
A good preparatory practice is kaya sthairyam.
Do khechari mudra and ujjayi pranayama.
Become aware of the breathing process.
Make the breathing longer and deeper.
Maintain complete attention on the breath.
It is most important to know that you are doing the practice.
Know that the breathing process is taking place.
After a few minutes feel the breath moving between navel and throat.
Inhalation ascending from the navel to the throat.
Exhalation descending from throat to navel.
Be totally aware of the breathing process; this is essential.
After a few minutes synchronize the sound So with inhalation and Ham with exhalation. Let the mantra be an endless repetition: SoHam-So-Ham-So-Havi . . .
So should merge with Ham and Ham should merge with So.
These two sounds should not be regarded as separate but as continuations of each other.
The last part of So joins with Ham.
The last part of Ham joins with So.
The So sounds on the upward cycle of breath
from the navel; towards the end of the cycle before reaching the throat, the sound of Ham should begin.
The sound Ham occurs on the downward cycle of exhalation from the throat; towards the end of the cycle, just before the navel, the sound So should begin.
Halfway through So turn your attention to Soham and halfway through Ham turn your attention to Hamso.
In this manner, the mantra Soham becomes an unbroken sound … the mantra and breathing become a constant stream.
There should be no break.
Carry on in this manner for a few minutes, about 5 minutes.
Then practise chidakasha dharana.
Watch the space in front of the closed eyes.
Merely be a witness to whatever arises, if anything, on the mind screen.
Alter about 3 minutes, return to the practice of ajapa: awareness of the mantra and respiration.
After another 5 minutes, again repeat chidakasha dharana.
Continue to alternate between ajapa and chidakasha dharana for the duration of the time that you assigned for your practice.