The special practice of channeling the breath involves a meditation with three sets of three inhalations and exhalations from each nostril; that is, from each nostril separately and then with both nostrils together.

Each of the three sets is the same except that its source is different. The first set is three inhalations through one nostril and three exhalations through the other; the second set is three inhalations through the second nostril and three exhalations through the first nostril; and the third set is three inhalations and exhalations using both nostrils together.

The first exhalation of each set is forceful and also very long and drawn out. The second is also forceful but it is short.  The third is gentle and drawn out, natural, without any force or special exertion behind it. Do this three times from the one nostril, then repeat it with the other nostril, then once again with both.

Now, when the breathing is forceful, you don’t just force it out all at once. You begin very gently, very slowly, increasing it more and more; making it very strong in the middle, and trail off with it again gently.

These breaths are said to be like the quill of a porcupine. The porcupine quill is very sharp and fine at either end and big in the middle.  So that’s how these breaths should be start out gently, quickly get stronger and stronger, and then trail off. The reason for this is that there are many very small, fine channels for the breath. Rather than strain them all at once, which wouldn’t be effective, you follow their subtlety by starting off gently so they will open up. If you force the breath out all at once there is a danger that they will not open or that these fine, subtle channels could be harmed. As you inhale, your lungs fill up completely. Once they are completely filled, pause, and then do the exhalation.