Adeptship is achieved by purification of Man’s Three bodies. It is also attainable through the Grace of the Guru.
Purification comes through Nature, penance, and mantras.
Through Nature, there is purification of dense matter (the physical body); through penance, purification of the fine matter (the subtle body); through mantras, purification of the mind.
… the process of how these purifications can be effected may be learned at the feet of the divine personages who witness light and bear testimony of the Christ Consciousness.
Source: Chapter 4, Sutras 1 – 3, Revelation from ‘The Holy Science (Kaivalya Darshanam)’ by Sri Yukteshwar Giri