Patanjali and Yoga Sutras
"In the Yoga-sutra of Patanjali, the soul is called pratyag-atma and parag-atma. As long as the soul is attached to sense enjoyment, it is called parag-atma. The soul is subjected to the functions of ten kinds of air at work within the body, and this is perceived through the breathing system. The Patanjali system of yoga instructs one on how to control the functions of the body's air in a technical manner so that ultimately all the functions of the air within become favorable for purifying the soul of material attachment. According to this yoga system, pratyag-atma is the ultimate goal. This pratyag-atma is a withdrawal from activities in matter. The senses interact with the sense objects, like the ear for hearing, eyes for seeing, nose for smelling, tongue for tasting, hand for touching, and all of them are thus engaged in activities outside the self. They are called the functions of the prana-vayu. The apana-vayu goes downwards, vyana-vayu acts to shrink and expand, samana-vayu adjusts equilibrium, udana-vayu goes upwards--and when one is enlightened, one engages all these in searching for self-realization."
Bhagavad-gita 4:27 Purport
"Yoga practice is more or less based on the principles of the Patanjali system. Some unauthorized commentators try to identify the individual soul with the Supersoul, and the monists think this to be liberation, but they do not understand the real purpose of the Patanjali system of yoga. There is an acceptance of transcendental pleasure in the Patanjali system, but the monists do not accept this transcendental pleasure, out of fear of jeopardizing the theory of oneness. The duality of knowledge and knower is not accepted by the nondualist, but in this verse transcendental pleasure--realized through transcendental senses--is accepted. And this is corroborated by Patanjali Muni, the famous exponent of the yoga system. The great sage declares in his Yoga-sutras (3.34): purusartha-sunyanam gunanam pratiprasavah kaivalyam svarupa-pratistha va citi-saktir iti.
This citi-sakti, or internal potency, is transcendental. Purusartha means material religiosity, economic development, sense gratification and, at the end, the attempt to become one with the Supreme. This "oneness with the Supreme" is called kaivalyam by the monist. But according to Patanjali, this kaivalyam is an internal, or transcendental, potency by which the living entity becomes aware of his constitutional position. In the words of Lord Caitanya, this state of affairs is called ceto-darpana-marjanam, or clearance of the impure mirror of the mind. This "clearance" is actually liberation, or bhava-maha-davagni-nirvapanam. The theory of nirvana--also preliminary--corresponds with this principle. In the Bhagavatam (2.10.6) this is called svarupena vyavasthitih. The Bhagavad-gita also confirms this situation in this verse."
"The yoga system described in the books of Patanjali is authoritative, and the modern so-called yogis who have manufactured their own ways, not consulting the authorities, are simply ludicrous. The Patanjali yoga system is called astanga-yoga. Sometimes impersonalists pollute the Patanjali yoga system because they are monists. Patanjali describes that the soul is transcendentally pleased when he meets the Supersoul and sees Him. If the existence of the Supersoul and the individual is admitted, then the impersonalist theory of monism is nullified. Therefore some impersonalists and void philosophers twist the Patanjali system in their own way and pollute the whole yoga process.
According to Patanjali, when one becomes free from all material desires he attains his real, transcendental situation, and realization of that stage is called spiritual power. In material activities a person engages in the modes of material nature. The aspirations of such people are (1) to be religious, (2) to be economically enriched, (3) to be able to gratify the senses and, at last, (4) to become one with the Supreme. According to the monists, when a yogi becomes one with the Supreme and loses his individual existence, he attains the highest stage, called kaivalya. But actually, the stage of realization of the Personality of Godhead is kaivalya. The oneness of understanding that the Supreme Lord is fully spiritual and that in full spiritual realization one can understand what He is--the Supreme Personality of Godhead--is called kaivalya, or, in the language of Patanjali, realization of spiritual power. His proposal is that when one is freed from material desires and fixed in spiritual realization of the self and the Superself, that is called cit-sakti. In full spiritual realization there is a perception of spiritual happiness, and that happiness is described in Bhagavad-gita as the supreme happiness, which is beyond the material senses. Trance is described to be of two kinds, samprajnata and asamprajnata, or mental speculation and self-realization. In samadhi or asamprajnata one can realize, by his spiritual senses, the spiritual form of the Lord. That is the ultimate goal of spiritual realization.
According to Patanjali, when one is fixed in constant realization of the supreme form of the Lord, one has attained the perfectional stage, as attained by Kardama Muni. Unless one attains this stage of perfection--beyond the perfection of the preliminaries of the yoga system--there is no ultimate realization. There are eight perfections in the astanga-yoga system. One who has attained them can become lighter than the lightest and greater than the greatest, and he can achieve whatever he likes. But even achieving such material success in yoga is not the perfection or the ultimate goal. The ultimate goal is described here: Kardama Muni saw the Supreme Personality of Godhead in His eternal form. Devotional service begins with the relationship of the individual soul and the Supreme Soul, or Krsna and Krsna's devotees, and when one attains it there is no question of falling down. If, through the yoga system, one wants to attain the stage of seeing the Supreme Personality of Godhead face to face, but is attracted instead to attainment of some material power, then he is detoured from proceeding further. Material enjoyment, as encouraged by bogus yogis, has nothing to do with the transcendental realization of spiritual happiness. Real devotees of bhakti-yoga accept only the material necessities of life absolutely needed to maintain the body and soul together; they refrain completely from all exaggerated material sense gratification. They are prepared to undergo all kinds of tribulation, provided they can make progress in the realization of the Personality of Godhead."
"The followers of the Patanjali yoga system actually want to merge into the body of the Supreme Personality of Godhead. This indicates that they do not want to engage in His service despite their knowledge of Him, and thus their position is even more abominable than that of those who want to merge into the Lord's effulgence. These yogis meditate on the four-handed Visnu form of the Lord in order to merge into His body. The Patanjali system describes the form of the Lord as klesa-karma-vipakasayair aparamrstah purusa-visesa isvarah: "The Supreme Personality of Godhead is a person who does not partake of a miserable material life." The yogis accept the eternity of the Supreme Person in one of their mantras--sa purvesam api guruh kalanavac-chedat: "Such a person is always supreme and is not influenced by the element of time." The followers of the Patanjali system therefore accept the eternity of the Supreme Personality of Godhead, yet, according to them: purusartha-sunyanam pratiprasavah kaivalyam svarupa-pratistha va citi-saktir iti. They believe that in the perfectional stage, the conception of purusa is vanquished. According to their description: citi-saktir iti. They believe that when one becomes perfect, he cannot remain a person. This yoga system is therefore abominable because its final conception is impersonal. In the beginning, these yogis accept the Supreme Personality of Godhead, but they ultimately give up this idea in order to become impersonal. They are most unfortunate because although they have a personal conception of the Absolute Truth, they neglect to render devotional service to the Lord and thus fall down again into the material world. This is supported by Srimad-Bhagavatam (10.2.32). Aruhya krcchrena param padam tatah patanty adho 'nadrta-yusmad-anghrayah: due to neglecting the lotus feet of the Lord, these yogis again fall down into the material existence (patanty adhah). Consequently this path of yoga is more abominable than the impersonalists' path. This conclusion is also supported by Lord Kapiladeva in the following verse from Srimad-Bhagavatam (3.29.13)."
Caitanya-caritamrta, Madyam lila 6:269
Bhaktivedanta Book Trust. HDG A.C. Bhaktivedanta Swami Srila Prabhupada.