Kundalini Yoga by Swami Sivananda (Sri Swami Sivananda Saraswati)
Oh Divine Mother Kundalini, the Divine Cosmic Energy that is hidden in men! Thou art Kali, Durga, Adisakti, Rajarajeswari, Tripurasundari, Maha-Lakshmi, Maha-Sarasvati! Thou hast put on all these names and forms. Thou hast manifested as Prana, electricity, force, magnetism, cohesion, gravitation in this universe. This whole universe rests in Thy bosom. Crores of salutations unto thee. O Mother of this world! Lead me on to open the Sushumna Nadi and take Thee along the Chakras to Sahasrara Chakra and to merge myself in Thee and Thy consort, Lord Siva.
Kundalini Yoga is that Yoga which treats of Kundalini Sakti, the six centres of spiritual energy (Shat Chakras), the arousing of the sleeping Kundalini Sakti and its union with Lord Siva in Sahasrara Chakra, at the crown of the head. This is an exact science. This is also known as Laya Yoga. The six centres are pierced (Chakra Bheda) by the passing of Kundalini Sakti to the top of the head.