The Siddha Yoga means Shaktipata Yoga: Transmission of Power
Following the (Maha Vakya) Great statements of the Vedas when a human being experiences communion with God (Brahma), it is called ‘Knowledge’. By the grace of God and by the favorable glance of the spiritual master a deserving disciple achieves this ‘Knowledge’ through the transmission of spiritual power. Although the Serpent Power (Kundalini Shakti) is all pervading and eternal it remains ensnared in the sinful deeds of the past many birts. By the grace of the spiritual master the sins commited by the initiated are uprooted and the dormant Serpent Power (Kundalini Shakti) becomes active. The layers over the Primal Power (Moola Shakti, i.e Kundalini) are removed and she merges into her original form of the divine entity, by the transmission of spiritual power. Owing to the awakening of the Serpent Power, the vital Life Force (Prana) rises upward and consequently mind and Life Force both merge into one completely. Hence this path is known as the Sidda Yoga or Maha Yoga.
Shaktipat : Transmission of spiritual power / Descent of spiritual energy upon an aspirant.
This path is of the type of restraint over tendencies of mind mentioned in Yoga Darshan by the Great sage Patanjali. This state of mind can be achieved spontaneously and instantly by the Grace of a spiritual master. The important difference between the Sidda Yoga and other yogic paths is that the followers of other yogic systems have to make strenuous efforts to accomplish the final goal, while one who has been initiated into Sidda Yoga experience automatic physical movements of all the four Yogas namely, Hatha, Mantra, Laya and Raja according to the requirements of his body, mind and accumulated impressions of past deeds. If an aspirant needs
Bandha, Mudra and Pranayama (breath control) to purify his mind, Prana and senses, these Yogic feets (movements), would happen automatically. If the aspirant needs mantra, he would receive it in a dream or through the divine utterances e.t.c. Likewise it is also observed that the spiritual progress of a devotee, absorbed in God’s worship is accelerated and he attains higher stages like Manonmani and A-manaska (higher thoughtless state of mind) due to Grace of the serpent power (Kundalini Shakti). It can stated firmly that for the complete purification of an aspirant’s mind and body, the serpent power (Kundalini) herself employs one or all the four ways of Yoga.
Guru-Tattwa (The power of the spiritual master)
The principle which makes the initiated feel the Direct experience of the transmission of power (Shaktipat) is the Guru-Principle. Preceptors of Vedas call this spiritual power, Chiti-Shakti, Yogis call her the Serpent Power (Kundalini), where as mantra-Yogis call her Mantra-Chaitanya.
-Siddha Yoga, Sree Loknath Tirth Swami Maharaj