When the observation is based on waking entity or ego then the universe seems to be reality. When observed on the base Soul, the innermost self the universe is mere mirage.

The source of the mind means the source of the universe,  because the mind is in the form of the universe.  Man and his experience of the world are within mind. Mind appears as waking or dream and disappears as deep sleep.  One perceives the world within the mind. 

When the observation is based on  waking entity or ego than the universe seems to be reality. When observed on the base Soul, the innermost self  than  the universe is mere mirage.  Thus one has to rectify his base of observation mentally from ego base to soul base,  than only it is possible to understand, assimilate and realize the non-dual truth.

The soul, is in the form of the consciousness. Consciousness  is the formless substance and witness of the three states.  Thus the soul is the source from where the universe rises as waking or dream and subsides as deep sleep.  The substance,witness and the source are one in essence.

Thus the self is within the universe and it is without the universe.  Discovering the source and substance and witness of the three states is very impotent in pursuit of truth or spirituality.

Spiritual pursuit is a very personal journey. Seeker of truth has to bifurcate everything which is based on the waking entity and waking experience, because the waking entity is false self within the false experience.  Religion, God, paths and theories and philosophy are based on the waking entity or ego ,which is the  false self  within the false experience. All such accumulated knowledge based on the false self is on not of any use in pursuit of truth.  

Seeker of truth should not indulge in condemning religion and yoga or its Gurus or Gods and it code of conduct. But he has to highlight its fallacy for his own information which helps him to proceed deeper in investigation.

Seeker of truth has to mingle and discuss with like-minded seekers but never indulge in arguments about religious doctrines and its ideas of god and remain in silent mode when the discussion is not on the right track when he is mingling with the people of different mind-set. 

Religion and god and guru glorification and scriptural studies or yoga are not needed in pursuit of truth. Only intense urge and courage to accept the truth and reject the untruth, when un-contraindicated truth is revealed through deeper self-search. 

Consciousness is formless substance and the witness of the three states is within the three states but it is beyond the three states. When the seeker realizes the truth then he realize the fact that in reality there is neither the witness nor the witnessed because both are one in essence.  Thus he is fully aware of the fact that, all the contents, forms and names of the waking or dream are mere mirage created out of consciousness.  This division created with forms and names are part of the mirage. There is no division in consciousness in reality.  The consciousness is indivisible reality.  

The ultimate state lies beyond the illusory experience of duality, since it is prior to it. One can only talk of duality or non-duality within the experience of duality. In non-duality is ultimate subject there is no second thing other than spirit or Atman in natural state.