Yogic Samadhi is not Advaitic wisdom of Sage Sankara.+

Sage Sankara in the commentary to "Brahma Sutras:- " "The highest beatitude is not to be attained by Yoga." (Sacred Books of East Series page 298 Vol.1.)  

Sage  Sankara says: ~Yoga is not the means of liberation (page 132-133 - Commentary on Brihadaranyakopanishad).

If yogis practice Yoga up to the limit and extent of getting a strong and concentrative mind, and to be able to think of particular subjects, it is good; beyond that, if they begin to weaken their mind and accept what they imagine as real, they begin to go insane.  The famous commentator on the key text The Manduka Upanishad.

Panchadesi: - the impossibility of yoga arrives at a successful end to its practices. (P.509 v, 109)

Yoga belief is a self-mesmeric condition out of which it is extremely difficult to escape. Yogic and mystic experiences are imaginations projected outwards as the dreamer projects his dream visions.

Bhagavan Buddha gave up his austerities of yoga as impossible and useless. (Page.70/71 "Buddhism in Translation” by Warren)

Bhagavan Buddha got enlightenment only after he gave up Yoga. Unless one exercises his reason--there is no chance of getting the truth.

When the yogi enters this highest Nirvikalpa (effort-less) Samadhi, he will at once enter deep sleep. This will make plain to him after he wakes, that the inner ‘Self’ he sought and found, the Atman, is reached only when all his ideas are refunded into it, when there is then all the features of non-duality, one without a second. However, the yogi must later wake up, emerge from Samadhi and there is duality again, for the world of objects confronts him. So now he has to work on the next stage which is to find consciously in the waking experience the same non-duality that he unconsciously knew in sleep. This is done by learning that a universe is an object for the formless subject, and then refunding the universe ~idea back into its source, which is the Soul, which is present in the form of the consciousness. Only at this final stage dare, he says "Atman, which is present in the form of the consciousness, is the same as the Brahman. Brahman is the ultimate truth.  Now he is fully aware of it.

All yogic visions, however, wonderful will pass away; they go as they come. They have the value of dreams. They are not the truth which is un-passing and beyond changes.

One can’t shut his eye to the universe, which confronts him as in Samadhi of yoga and see supreme reality. One can know it only by keeping himself clear and open.

 Sage  Sankara:~   The yogi must add discrimination to his quest.

Nirvikalpa Samadhi and deep sleep are the same from the standpoint of the Soul, the innermost ‘‘Self’’ the absence of the known. The knower was there.

How does Yogic Samadhi give Gnana? Only by preparing yourself to see that the world disappears and re-appears and, that non-duality is here and duality there, to convince the man that in non-duality one won't disappear as he doesn't disappear in Samadhi or deep sleep. Another advantage of Samadhi is one gets the capacity to forget the external world and to treat it as an idea.

Yoga can never give you the fundamental thing, that the world is an illusion. Only Gnana can give it. 

Nirvikalpa Samadhi is unquestionably the same as deep sleep, and all ideas are refunded back there too. One must learn what ideas are when all the ideas of the universe-existence go back into one’s mind through Yoga. Then one learns this. How has he to learn that the entire universe is consciousness or Brahman if he stops at Nirvikalpa Samadhi? Without perceiving the universe, and having a duality before him, it is impossible.

Nirvikalpa has no duality, hence it cannot tell you about the universe. The yogi who emerging from Samadhi and says he found Gnana there, says it to a second person, hence there is duality again. If he were a real Gnani, there would be nobody for him to tell that he had experienced Gnana.

‘Self’-knowledge will interest only a few people; the rest are interested in Religion, yoga other paths, and pleasure hunting.  : ~ Santthosh Kumaar