D: Of the means for mind-control, which is the most important?
M: Breath-control is the means for mind-control.
D: How is breath to be controlled?
M: Breath can be controlled either by absolute retention of breath (kevala-kumbhaka) or by regulation of breath (pranayama).
D: What is absolute retention of breath?
M: It is making the vital air stay firmly in the heart even without exhalation and inhalation. This is achieved through meditation on the vital principle, etc.
D: What is regulation of breath?
M: It is making the vital air stay firmly in the heart through exhalation, inhalation, and retention,according to the instructions given in the yoga texts.
D: How is breath-control the means for mind-control?
M: There is no doubt that breath-control is the means for mind-control, because the mind, like breath, is a part of air, because the nature of mobility is common to both, because the place of origin is the same for both, and because when one of them is controlled the other gets controlled.
D: Since breath-control leads only to quiescence of the mind (manolaya) and not to its destruction (manonasa), how can it be said that breath-control is the means for enquiry which aims at the destruction of mind?
M: The scriptures teach the means for gaining Self-realization in two modes—as the yoga with eight limbs (ashtanga-yoga) and as knowledge with eight limbs (ashtanga-jnana). By regulation of breath (pranayama) or by absolute retention thereof (kevala-kumbhaka), which is one of the limbs of yoga, the mind gets controlled. Without leaving the mind at that, if one practises the further discipline such as withdrawal of the mind from external objects (pratyahara), then at the end, Self-realization which is the fruit of enquiry will surely be gained.
D: What are the eight limbs of Yoga?
[Also see the eight limbs of Knowledge, question 34.]
M: Yama, niyama, asana, pranayama, pratyahara, dharana, dhyana, and samadhi. Of these—
(1) Yama:– this stands, for the cultivation of such principles of good conduct as non-violence (ahimsa), truth (satya), non-stealing (asteya), celibacy ( brahmacharya), and non-possession (apari-graha).
(2) Niyama:– this stands for the observance of such rules of good conduct as purity (saucha), contentment (santosha), austerity (tapas), study of the sacred texts (svadhyaya), and devotion to God (Isvara-pranidhana). 
(3) Asana:– Of the different postures, eighty-four are the main ones. Of these, again, four, viz., simha, bhadra, padma, and siddha  are said to be excellent. Of these too, it is only siddha, that is the most excellent. Thus the yoga-texts declare.
(4) Pranayama:– According to the measures prescribed in the sacred texts, exhaling the vital air is rechaka, inhaling is puraka and retaining it in the heart is kumbhaka. As regards "measure", some texts say that rechaka and puraka should be equal in measure, and kumbhaka twice that measure, while other texts say that if rechaka is one measure, puraka should be of two measures, and kumbhaka of four. By "measure" what is meant is the time that would be taken for the utterance of the Gayatrimantra [a] once. Thus pranayama consisting of rechaka, puraka, and kumbhaka, should be practised daily according to ability, slowly and gradually. Then, there would arise for the mind a desire to rest in happiness without moving. After this, one should practise pratyahara.
(5) Pratyahara:– This is regulating the mind by preventing it from flowing towards the external names and forms. The mind, which had been till then distracted, now becomes controlled. The aids in this respect are (a) meditation on the pranava, [the mantra Om] (b) fixing the attention betwixt the eyebrows, (c) looking at the tip of the nose, and (4) reflection on the nada. The mind that has thus become one-pointed will be fit to stay in one place. After this, dharana should be practised.
(6) Dharana:– This is fixing the mind in a locus which is fit for meditation. The loci that are eminently fit for meditation are the heart and Brahma-randhra (aperture in the crown of the head). One should think that in the middle of the eight-petalled lotus  that is at this place there shines, like a flame, the Deity which is the Self, i.e. Brahman, and fix the mind therein. After this, one should meditate.
(7) Dhyana:– This is meditation, through the "I am He" thought, that one is not different from the nature of the aforesaid flame. Even, thus, if one makes the enquiry "Who am I?", then, as the Scripture declares, "The Brahman which is everywhere shines in the heart as the Self that is the witness of the intellect," one would realize that is the Divine Self that shines in the heart as "I–I." This mode of reflection is the best meditation.
(8) Samadhi:– As a result of the fruition of the aforesaid meditation, the mind gets resolved in the object of meditation without harbouring the ideas "I am such and such; I am doing this and this." This subtle state in which even the thought "I–I" disappears is samadhi. If one practises this every day, seeing to it that sleep does not supervene, God will soon confer on one the supreme state of quiescence of mind.
D: What is the purport of the teaching that in pratyahara one should meditate on the pranava? [the mantra Om]
M: The purport of prescribing meditation on the pranava is this. The pranava is Omkara consisting of three and a half matras, viz., a, u, m, and ardha-matra. Of these, a stands for the waking state, Visva-jiva, and the gross body; u stands for the dream-state Taijasa-jiva, and the subtle body; m stands for the sleep-state, Prajnajiva and the causal body; the ardha-matra represents the Turiya which is the self or "I"-nature; and what is beyond that is the state of Turiyatita, or pure Bliss.
The fourth state [Turiyatita] which is the state of "I"-nature was referred to in the section on meditation (dhyana): this has been variously described as of the nature of amatra which includes the three matras, a, u, and m; as maunakshara (silence syllable); as ajapa (as muttering without muttering) and as the Advaita-mantra which is the essence of all mantras such as panchakshara. [Om Namah Shivaya]
In order to get at this true significance, one should meditate on the pranava. This is meditation, which is of the nature of devotion consisting in reflection on the truth of the Self. The fruition of this process is samadhi which yields release which is the state of unsurpassed bliss. The revered Gurus also have said that release is to be gained only by devotion which is of the nature of reflection on the truth of the Self.
D: What is the purport of the teaching that one should meditate, through the "I am He" thought, on the truth that one is not different from the self-luminous Reality that shines like a flame?
M: (A) The purport of teaching that one should cultivate the idea that one is not different from the self-luminous Reality is this: Scripture defines meditation in these words,
"In the middle of the eight-petalled heart-lotus which is of the nature of all, and which is referred to as Kailasa, Vaikundha, and Parama-pada, there is the Reality which is of the size of the thumb, which is dazzling like lightning and which shines like a flame. By meditating on it, a person gains immortality."
From this we should know that by such meditation one avoids the defects of (1) the thought of difference, of the form "I am different, and that is different," (2) the meditation on what is limited, (3) the idea that the real is limited, and (4) that it is confined to one place.
(B) The purport of teaching that one should meditate with the "I am He" thought is this: sahaham: soham; sah the supreme Self, aham the Self that is manifest as "I". The jiva which is the Shiva-linga resides in the heart-lotus which is its seat situated in the body which is the city of Brahman; the mind which is of the nature of egoity, goes outward identifying itself with the body, etc.
Now the mind should be resolved in the heart; i.e. the "I"-sense that is placed in the body, etc., should be got rid of. When thus one enquires "Who am I?", remaining undisturbed, in that state the Self-nature becomes manifest in a subtle manner as "I–I". That self-nature is all and yet none, and is manifest as the supreme Self everywhere without the distinction of inner and outer. That shines like a flame, as was stated above, signifying the truth "I am Brahman." If, without meditating on that as being identical with oneself, one imagines it to be different, ignorance will not leave. Hence, the identity-meditation is prescribed.
If one meditates for a long time, without disturbance, on the Self ceaselessly, with the "I am He" thought which is the technique of reflection on the Self, the darkness of ignorance which is in the heart and all the impediments which are but the effects of ignorance will be removed, and the plenary wisdom will be gained. 
Thus, realizing the Reality in the heart-cave which is in the city (of Brahman), viz. the body, is the same as realizing the all-perfect God.
In the city with nine gates, which is the body, the wise one resides at ease. 
The body is the temple; the jiva is God (Shiva). If one worships him with the "I am He" thought, one will gain release.
The body which consists of the five sheaths is the cave; the supreme that resides there is the lord of the cave. Thus the scriptures declare.
Since the Self is the reality of all the gods, the meditation on the Self which is oneself is the greatest of all meditations. All other meditations are included in this. It is for gaining this that the other meditations are prescribed. So, if this is gained, the others are not necessary. Knowing one's Self is knowing God. Without knowing one's Self that meditates, imagining that there is a deity which is different and meditating on it, is compared by the great ones to the act of measuring with one's foot one's own shadow, and to the search for a trivial conch after throwing away a priceless gem that is already in one's possession. 
D: Even though the heart and the Brahmarandhra [Crown Chakra] alone are the loci fit for meditation, could one meditate, if necessary, on the six mystic centres (adharas)?
M: The six mystic centres, etc., which are said to be loci of meditation, are but products of imagination. All these are meant for beginners in yoga. With reference to meditation on the six centres, the Shiva-yogins say,
And the Vedantins declare, "All those are but imaginations of the mind."
Therefore, if one knows one's Self which is of the nature of consciousness that knows everything, one knows everything. The great ones have also said: "When that One is known as it is in Itself, all that has not been known becomes known." If we who are endowed with various thoughts meditate on God that is the Self we would get rid of the plurality of thoughts by that one thought; and then even that one thought would vanish. This is what is meant by saying that knowing one's Self is knowing God. This knowledge is release.