After having secured stability in the Āsanas the prāṇāyāmas should be attempted. The pause that comes after a deep inhalation and that after a deep exhalation are each called a prāṇāyāma; the first is external, the second internal. There is, however, a third mode, by means of which, since the lungs are neither too much dilated nor too much contracted, total restraint is obtained; cessation of both these motions takes place by a single effort, just as water thrown on a heated stone shrivels up on all sides. These can be regulated by calculating the strength of inhalation and exhalation through space, time or number. Thus as the breathing becomes slower, the space that it occupies also becomes smaller and smaller. Space again is of two kinds, internal and external. At the time of inhalation, the breath occupies internal space, which can be felt even in the soles of hand and feet, like the slight touch of an ant. To try to feel this touch along with deep inhalation serves to lengthen the period of cessation of breathing. External space is the distance from the tip of the nose to the remotest point at which breath when inhaled can be felt, by the palm of the hand, or by the movement of any light substance like cotton, etc., placed there. Just as the breathing becomes slower and slower, the distances traversed by it also becomes smaller and smaller. Regulations by time is seen when the attention is fixed upon the time taken up in breathing by moments, a moment (_kshaṇa_) is the fourth part of the twinkling of the eye. Regulation by time thus means the fact of our calculating the strength of the prāṇāyāma the moments or kshaṇas spent in the acts of inspiration, pause and respiration. These prāṇāyāmas can also be measured by the number of moments in the normal duration of breaths. The time taken by the respiration and expiration of a healthy man is the same as that measured by snapping the fingers after turning the hand thrice over the knee and is the measure of duration of normal breath; the first attempt or udghāta called mild is measured by thirty-six such mātrās or measures; when doubled it is the second udghāta called middling; when trebled it is the third udghāta called intense. Gradually the Yogin acquires the practice of prāṇāyāma of long duration, by daily practice increasing in succession from a day, a fortnight, a month, etc. Of course he proceeds first by mastering the first udghāta, then the second, and so on until the duration increases up to a day, a fortnight, a month as stated. There is also a fourth kind of prāṇāyāma transcending all these stages of unsteady practice, when the Yogin is steady in his cessation of breath. It must be remembered, however, that while the prāṇāyāmas are being practised, the mind must be fixed by dhyāna and dhāraṇā to some object external or internal, without which these will be of no avail for the true object of Yoga. By the practice of prāṇāyāma, mind becomes fit