Mouni Maharaj:
"Yoga means to merge with Spirit. The only way to the Spirit is through the Deepmental (Celestial).
The only way to the Deepmental is through the Deepemotional (Astral). The only way to the Deepemotional is through the Deepbody (Etheric) and the way to the Deepbody is through the physical body.
There is no other way to the Spirit."
Yoga system
Initially, on an outer level, students are taught some physical exercises "Yoga postures" along with some bodily cleansing procedures. This period of 4 or 5 years tests the students determination to learn and their willingness to follow.
Yoga - 1st Level
The first step into the internal is through breathing. Breathing is the only purely instinctive function easily influenced by the superficial-mind. Concentrating first on awareness of breathing and later on breathing control begins the process of the mind going deeper, which involves both the reduction of the excessive brain activity and the arising of the first level of the Deep Mind. From breathing the student is led to more subtle instinctive processes such as awareness and control of heartbeat, pulse, body temperature and muscles concerned with internal functions rather than external movement. Typically this stage may take 10 years of concentrated effort to complete, fixing the mind on the etheric level.
Yoga - 2nd Level
This is concerned with energy awareness and control, beginning with the etheric, concentrated within the astral and leading to the celestial. Concentration - initially with awareness but later with a strong effort of will - on the energy centres and pathways of the body, leads to the 'raising of the kundalini' and final escape from the body and etheric levels into the astral. Attempting this level before the mind has sunk to the etheric levels of the previous stage, only leads to imagination as the superficial-mind becomes involved. While no set time is required, typically again 10 years or more would be needed to stabilise on this level
Yoga - 3rd Level
This concerns the Deep Mind Intelligence which is the connection of the Spirit into the celestial sphere. Little is to be done at this stage except to aspire or reach out to the Beyond and wait while the Beyond does its work. Completion of this carries a person into the 4th energy level, earthly exercises lose their importance and progress is managed mostly by the Spirit from that time on.
