"within the Self, in the innermost"

The concept of Self is closely connected with the concept of Atman, 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 a beings original nature - satyam, shivam, sundaram - truth, consciousness, bliss. 

The Taittiriya Upanishad explains how the Self (Atman) is encased in five layers or sheaths: the physical body, the life force, mind, intelligence, and bliss. The aim of this meditation is to observe the layers and become still to be able to manifest the pure consciousness of the Self. This is realization of the Self, the innermost Being.