Swami Vivekananda on Kundalini Yoga
When by the power of long internal meditation the vast mass of energy storedup travels along the sushumna and strikes the centers, the reaction is tremendous, immensely superior to the reaction of dream or imagination, immensely more intense than the reaction of sense-perception.
Wherever there was any manifestation of what is ordinarily called supernatural power or wisdom, there a little current of kundalini must have found its way into the sushumna. Only, in the vast majority of such cases, people had ignorantly stumbled on some practice which set free a minute portion of the coiled up kundalini.All worship, conciously or unconciously, leads to this end. The man who thinks that he is receiving response to his prayers does not know that the fulfillment comes from his own nature, that he has succeeded by the mental attitude of prayer in waking up a bit of this infinite power which is coiled up within himself.
What, thus, man ignorantly worships under various names, through fear and tribulation, the yogi declares to the world to be the real power coiled up in every being, the mother of eternal happiness, if we but know how to approach her. And yoga is the science of religion, the rationale of all worship, all prayers, forms, ceremonies and miracles.
An online biography and Complete Works of Swami Vivekananda is available here.