From Yoga for Yahoos

Pranayama means control of force. It is a generalised term. In the Hindu system there are quite a lot of subtle sub-strata of the various energies of the body which have all got names and properties. I do not propose to deal with the bulk of them. There are only two which have much practical importance in life. One of these is not to be communicated to the public in a rotten country like this; the other is the well-known 'control of breath.'

This simply means that you get a stop watch, and choose a cycle of breathing out and breathing in. Both operations should be made as complete as possible. The muscular system must be taxed to its utmost to assist the expansion and contraction of the lungs. When you have got this process slow and regular, for instance, 30 seconds breathing out and 15 in, you may add a few seconds in which the breath is held, either inside or outside the lungs.

(It is said, by the way, that the operation of breathing out should last about twice as long as that of breathing in, the theory being that breathing out quickly may bring a loss of energy. I think there may be something in this.)

There are other practices. For instance, one can make the breathing as quick and shallow as possible. Any good practice is likely to produce its own phenomena, but in accordance with the general thesis of these lectures I think it will be obvious that the proper practice will aim at holding the breath for as long a period as possible-because that condition will represent as close an approximation to complete stillness of the physiological apparatus as may be.

Of course we are not stilling it; we are doing nothing of the sort. But at least we are deluding ourselves into thinking that we are doing it, and the point is that, according to tradition, if you can hold the mind still for as much as twelve seconds you will get one of the highest results of Yoga.

It is certainly a fact that when you are doing a cycle of 20 seconds out, 10 in, and 30 holding, there is quite a long period during the holding period when the mind does tend to stop its malignant operations.

And so? Yes. Pranayama may be described as nice clean fun. Before you have been doing it very long, things are pretty certain to begin to happen, though this, I regret to remark, is fun to you, but death to Yoga.

The classical physical results of Pranayama are usually divided into four stages:

1. Perspiration. This is not the ordinary perspiration which comes from violent exercise; it has peculiar properties, and I am not going to tell you what these are, because it is much better for you to perform the practices, obtain the experience, and come to me yourself with the information. In this way you will know that you have got the right thing, whereas if I were to tell you now, you would very likely imagine it.
2. Automatic rigidity: the body becomes still, as the result of a spasm. This is perfectly normal and predictable. It is customary to do it with a dog. You stick him in a bell-jar, pump in oxygen or carbonic acid or something, and the dog goes stiff. You can take him out and wave him around by a leg as if he were frozen. This is not quite the same thing, but near it.
3. The third stage is marked by Buchari-siddhi: 'the power of jumping about like a frog' would be a rough translation of this fascinating word. This is a very extraordinary phenomenon. You are sitting tied up on the floor, and you begin to be wafted here and there, much as dead leaves are moved by a little breeze. This does happen; you are quite normal mentally, and you can watch yourself doing it.
   The natural explanation of this is that your muscles are making very quick short spasmodic jerks without your being conscious of the fact. The dog helps us again by making similar contortions. As against this, it may be argued that your mind appears to be perfectly normal. There is, however, one particular point of consciousness, the sensation of almost total loss of weight. This, by the way, may sound a little alarming to the instructed alienist. There is a similar feeling which occurs in certain types of insanity.
4. The fourth state is Levitation. The Hindus claim that 'jumping about like a frog' implies a genuine loss of weight, and that the jumping is mainly lateral because you have not perfected the process. If you were absolutely balanced, they claim that you would rise quietly into the air.  I do not know about this at all. I never saw it happen. On the other hand, I have often felt as if it were happening; and on three occasions at least comparatively reliable people have said that they saw it happening to me. I do not think it proves anything.