AUM has been revered as the perfect Symbol of absolute consciousness.

AUM

Aum heard itself,
and it was
Aum.
I am the beginning
I am the waking!
I am the now
I am the dreaming
and in the end,
I am the sleeping!
All is Aum!
Yet, Aum is more,
The being, withdrawal, and the making,
Aum is all four.

{Bhasya: From the time of the Upanishadic rishi, AUM has been revered as the perfect Symbol of absolute consciousness.}