Nirvikalpa Samadhi, which is identical to deep sleep.+

Manduka Upanisad:~ Those who want the ultimate truth or Brahman will not practice control of the mind. (p.231) 

Manduka Upanishad:~ Yoga is in the sphere of duality and is unnecessary to one who knows non-duality.The eye cannot see it; the mind cannot grasp it. The deathless Self has neither caste nor race, neither eyes not ears nor hands nor feet. Sages say this Self is infinite in the great and in the small, everlasting and changeless, the source of life. 

It is impossible to stop thought for more than a second whilst in the waking experience. If one succeeds in controlling thought and then banishes it, one passes into Nirvikalpa Samadhi, which is identical to deep sleep.

The only difference between ordinary deep sleep and Samadhi, therefore, is that the ordinary man falls asleep involuntarily, whereas the yogi has the satisfaction of knowing that he has passed into sleep by his own effort of will in banishing thoughts.

Yoga can yield the only duality, because, everything that one can do or practice becomes a vanishing 'known.' It yields relative truth based on imagination, which is true from a physical viewpoint of view, not the non-dualistic or Advaitic truth, which is the ultimate reality.

The yogic truth is the individual truth, not universal. The "Religions place God as the unknown reality.” Every religious believer has a different idea of God. Every man has a different idea of reality. Hence, the need for a definition before the study.

The yogic teachings about the six chakras and the seven chakras of Raja yoga are based on fact and fiction. It was noted that there were nervous plexuses and nodules at intervals in the spine and other parts of the body. Upon this basis, the yogis started imagining that if the ego is concentrated on each one, a different mystic result would be obtained. But that is mere fancy.

Manduka Upanishads: - Those who want Brahman will not practice control of the mind. That is Yoga for duffers. The others will inquire and practice discrimination. (p.231) : ~ Santthosh Kumaar