Lord Krishna says:~ This yoga has been lost for ages" the word yoga refers to Gnana yoga, not other yogas.+

If you are seeking truth then you must know that yoga is not the means to realize the truth, which is beyond form, time, and space. Unless one exercises Soulcentric reason there is no chance of getting the ultimate truth or Brahman.

Panchadasi, P.509 v, 109, shows the impossibility of yoga arriving at a successful end to its practices. 

The notion of Self-realization through yoga is not philosophic. Every yogi who shuts himself in a cave is not thereby freed from thinking. 

Yoga can lead only to temporary peace because the world is subject to change. Only Self- knowledge or Brahma Gnana or Atma Gnana can yield Advaitic awareness in the midst of the form, time, and space. 

Buddha gave up yoga after practicing it for six years. He saw it could not yield truth.

Buddha gave up his austerities of yoga as impossible and useless. Thus Buddha got enlightenment only after he gave up Yoga. (Page.70/71 "Buddhism In Translation” by Warren)

Yogis say, ‘I am not the body’ but they believe in body-based practices. The Soul is bodiless because it is a formless, timeless, and spaceless existence.  Without the body where are the chakras and where is the kundalini.

Yogi thinks the Self is within his body. The Soul, the ‘Self ‘is not within the body because it pervades form, time, and space.

All the yogic theories are limited to form, time, and space whereas the Soul, the Self is a formless, timeless, and spaceless existence.

Kundalini is based on the physical form. Kundalini requires the physical form.  Without the physical form, there is no kundalini. The physical form is not the ‘Self’.  The ‘Self’ is the Soul, which is present in the form of consciousness.

From the standpoint of the Soul, the ‘Self’ the form, time, and space is merely an illusion. Thus, all the theories based on form, time, and space are bound to be illusory theories based on the false self (form) within the dualistic illusion.

A yogi cannot attain realization because he thinks his body to be the body and the world to be the world and fails to see them as consciousness and thinks his experience of Samadhi is because of his individual effort. The individual experience is limited to waking experience is merely an illusion. 

Thus even his Samadhi is also limited to the waking experience, which is merely an illusion. He thinks the thoughtlessness is Samadhi but thoughts are of individuality. Thoughts disappear even in deep sleep. Therefore deep sleep is not wisdom. If one thinks thoughtlessness is Samadhi and Samadhi is Brahman then anyone gets knowledge of Brahman by taking sleeping pills or hemp.

Brih Upanishad: page 32:~  "Yoga does not yield truth or liberation."

One who is in Samadhi will not know that this universe as the consciousness; therefore yoga is not the means to Self- knowledge or Brahma Gnana or Atma Gnana.

 In Samadhi the yogi knows nothing and sees no universe; so if there is nothing but blankness. The blankness is not the Advaitic wisdom.

The yogi does not know the nature of the universe. If the universe is not seen in the Samadhi then there is no need to use the word Atman and Brahman.  The yogi is unaware of the truth, which is beyond form, time, and space. 

By shutting his eyes in Samadhi, the yogi does not know the universe, which confronts him. Hence the universe can't be known as the Soul or the consciousness through yoga.

One is in a non-dual condition in deep sleep or Samadhi, One without a second, true, but he did not know it at the time. He says only in the waking experience afterward. Hence, there must be an inquiry so that you find non-duality whilst you are awake so that you can see nonduality at the time not afterward. Hence, too the need of inquiring into the nature of the universe and knowing it as the Soul or consciousness whilst one is awake, and not during sleep or Samadhi.

Advaitic truth is the ultimate truth.  Yogis, mystics, and religious teachers do not accept the path of wisdom because it pries into the truth, the source, and the validity of the knowledge they claim. Therefore, it is the most difficult part of the study of Advaita.

That is why Sage Sankara said:~ Without causing the objective universe to vanish and without knowing the truth of the Self, how is one to achieve Liberation. -63- (VC)” 

The universe in which we exist will not remain as reality when wisdom dawns. The universe is merely an illusion created out of consciousness and there is a conscious awareness of unity in diversity because there is no second thing that exists other than consciousness.

Lord Krishna confesses that the oldest wisdom of India (Advaitic wisdom) has been lost: people misinterpret and falsify it today as they did then. It is not yoga but the philosophic truth. But nobody knows it. The teachers of philosophy and leaders of mysticism or religion do not want to inquire into truth and have no time for it. (Gita –Chap- IV-v.2)

In Gita Chap.IV where Lord Krishna says:~ "This yoga has been lost for ages" the word yoga refers to Gnana yoga, not other yogas: the force of the word this is to point this out.

Lord Krishna describes some of the other yogas but devotes this chapter separately to Gnana Yoga. So one sees even in those ancient days people did not care for Advaita; they wanted religion; hence Gnana got lost. That is why Krishna calls it "the supreme secret." Krishna points out that yoga must see "Brahman in action."   : ~ Santthosh Kumaar