The three-Dharana, Dhyana and Samadhi-together constitute Samyama. Samyama is the name given to the combined practice of Dharana, Dhyana and Samadhi at one and the same time. By Samyama on external objects the Yogi gets various Siddhis and hidden knowledge of the universe of Tanmatras, etc. By concentration on Indriyas, Ahankara, mind, etc., he gets various powers and experiences.
These three (Dharana, Dhyana and Samadhi) are more internal than the preceding Yama, Niyama, Asana, Pranayama and Pratyahara. These three constitute the Yoga proper. The five accessories are the external means of Yoga. These three directly bring Samadhi. The other five purify the body, Prana and Indriyas. Hence these three are called Antaranga Sadhana.
By the conquest of Samyama comes the stage of cognition. As Samyama becomes firmer and firmer, so does the knowledge of Samadhi become more and more lucid. This is the fruit of the practice of Samyama. Samyama should become very natural. Then the knowledge flashes like anything. Samyama is a powerful weapon for the Yogi. Just as the archer aims at the gross objects at first and then takes to subtle objects he does great deal of practice and ascends the Yogic ladder rung by rung.
By Samyama on the sun comes the knowledge of the worlds. By Samyama on the moon, comes the knowledge of the region of stars. By Samyama on the Pole Star, comes the knowledge of the movements of the starts. By Samyama on the strength of elephants and others, comes their strength.
By Samyama on the signs (of others), comes the knowledge of their minds. By Samyama on the relation of the ear and ether, comes the divine hearing. By Samyama on the relation between ether and body, to the Yogi attaining the lightness of cotton, comes the power of passage through ether (air).
By Samyama and direct perception of the Samskaras (impressions of mind), comes the knowledge of the previous birth. By Samyama on the distinctive relation between Sattva (purity) and Purusha (the soul), comes the power of omnipotence and omniscience. By Samyama on the Chakra (plexus) of navel, comes the knowledge of the body.
By Samyama on the Chakra at the pit of the throat, comes the removal of hunger and thirst. By Samyama on the light of the head, comes the Darshan of Siddhas.