BG Chap 8 - The process of yoga
He who leaves his body, while withdrawing his senses from sense objects, concentrating the mind on the Lord in the heart, fixing the prāṇa (life air) at the ajñā-cakra (top of his head), completely absorbing his thoughts on the Lord, uttering oṁ and meditating on the Lord constantly, attains His planet. One should control all the external doors of knowledge (the senses such as the ear), withdrawing them (pratyāhāra) from the sense objects such as sound, and receive the sense objects by senses disinterested in enjoyment by repeatedly seeing their faults. But even in controlling the senses, the mind will wander. So one needs to control the mind, which is the door to internal knowledge, upon the Lord, situated in the heart. Then one should control the life air, the door to actions, in the lotus of the heart, and then as one gains control, establish it at the top of the head on the path of the suṣumna moving upwards, under the instruction of the guru. Doing this, one should practice thinking of the Lord with complete absorption. One should utter oṁ and meditate on the Paramātmā (Brahman according to Viśvanātha) indicated by that sound. Meditating in this way, he attains the liberation of sālokya. This indicates that oṁ, Brahman and Kṛṣṇa are not different. Thus the yoga-miśra-bhaktas attain sālokya liberation.