Akshi Upanishad is a minor Upanishad dealing with yoga. It consists of 50 Sanskrit verses in anustubha (eighteen-syllabled) meter. It is assigned to the period before the 10th century CE. The sun, as per this Upanishad, is the traditional guru who teaches yogic knowledge or cakshushmati vidya (knowledge through the organ of the eye).
The sun is traditionally considered to be the deity of the
eye-organ. He reveals the seven stages of this yoga (sapta Bhumika yoga), to
Samskriti, a deity, pleased by the latter’s prayers. The first three stages are
grouped into the jagrata (wakeful) state of consciousness. These three stages
include details of the practices to be adopted for a moral and disciplined lifestyle by the aspirant. The fourth stage is linked to the Svapna (dreaming)
state of consciousness. The fifth state relates to sushupti (deep sleep), while
the sixth is linked to Turiya (the transcendental state). The final experience
is a description of Advaita (the unity) with the Supreme.
The philosophy of this Upanishad can be described as a
combination of spiritual experience and devotion to Bhagavan Vasudeva.