For those who are interested, the Mundaka Upanishad depicts precisely the relationship between innermost being and the outer self described in my previous post.
MANTRA NO. 1:
Two birds living together, each the friend of the other, perch upon the same tree. Of these two, one eats the sweet fruit of the tree, but the other simply looks on without eating.
MANTRA NO. 2:
In the self-same tree the individual (bird) is drowned in grief because of delusion and impotency. When it beholds the other (bird), viz., the adorable Lord, it realises its own glory and gets freed from sorrow.
MANTRA NO. 3:
When the knowing individual has the vision of the intelligent creator, the Lord, the Purusha, the Brahman which is the source of all, then it shakes off both merit and demerit, and having become taintless, attains to supreme equality with the Lord.
MANTRA NO 4:
In all beings this one supreme life manifests itself. Knowing this, the wise one does not speak of anything else. Having his sport in the Self, bliss in the Self, and action in the Self, he is the best among the knowers of Brahman.
MANTRA NO. 5:
The Atman is attained through truth, penance, correct knowledge and Brahmacharya (self-control), observed continuously without break. The Atman is beheld within in the form of light and purity by the austere ones who are freed from all kinds of sins.
MANTRA NO. 6:
Truth alone triumphs; not falsehood. Through truth the divine path is spread out by which the sages whose desires have been completely fulfilled, reach to where is that supreme treasure of Truth.
MANTRA NO. 7:
That which is supremely expansive, divine, of unthinkable form, subtler than the subtle, much farther than that which is far, and at the same time very near, shines and is seated in the Central Being of those who have the consciousness of That.
MANTRA NO. 8:
It is not grasped by the eye, not even by speech, nor by the other senses. It is not possible to know it through mortifications or deeds. He who meditates upon it with absolute purity (Sattva) of mind, as the partless Being, beholds it through the serenity attained in knowledge.
MANTRA NO. 9:
This subtle Atman should be known with the purified mind into which the Prana with its fivefold aspect has entered. The mind is pervaded completely by the functions of the Pranas together with the powers of the senses. In this purified mind this Atman is revealed.
MANTRA NO. 10:
Whichever region is thought of by the mind and whatever desires the man of purified mind desires, that region and those desires he obtains. Therefore, one who wishes to have prosperity should worship the knower of the Self.