"Already he knew how to recognize Atman"

Ātman (Sanskrit: आत्मन्) is a term used in Vedanta Hindu philosophy to identify the Universal Spirit - macrocosmic as well as microcosmic. Generally translated into English as 'Self,' it is the immortal aspect of the mortal existence, the element, the force, the indestructible energy that is hidden in every object of creation including man. It is the divine in all of us, the part of the macrocosms that encompasses the entire universe.

Some texts, describe the Atman as a flame, of the size of thumb, which exists between the eye brows (anatomically, the location of the pineal gland), or in the heart of all as an emotion, but its exact form and location is uncertain.

"The soul is not born; it does not die; it was not produced from anyone... Unborn, eternal, it is not slain, though the body is slain."   - Katha Upanisad

In Mandukya Upanishad, the self is described as fourfold:

"The wakeful Vaishwanara, the Universal Male (the ego),

The dreaming Taijasa, the enjoyer of subtle objects and the Lord of the luminous mind, (the astral),

The mysterious Pragna, the deep Sleeper and the Lord of Wisdom and

Atman the eternal, the Incommunicable, the end of phenomena, Brahman Itself."

The Self or Atman can be experienced only when the five senses cease to impact the mind, and the mind is free of thoughts and desires.  The practice of Yoga can help a person to attain this state of Oneness, where the Atman can be realized.