Pathanjali Yoga sutra
Tatra pratyaya ikatanata dhyanam
Tadevartha matra nirbhasam svarupa sunyam iva samadhih
Vibhuthipada explains the internal aspects of Yoga through Dharana and Samadhi. Before going into the glories of Yoga (Kaivalya pada), you need this internal aspect of the conscious internal mind that is anthakarana. (The mind consisting at various levels of mano, buddhi, ahankar, chitta, and anthakarana). This is called the Dharmendriya: one pointed focus of attention with thorough thoughtfulness on a focal point (a region or a spot) either within the body or outside. Sadhana and samadhi explains the way, the means, and the purpose of utilizing yoga. This chapter explains the glorious properties that occur through the mastery of yoga. One can focus outside by focusing on the manipura (the naval centre), Anahata (the heart centre), Agna (at the tip of the nose), or tip of the tongue.
If the above thorough thought flow of attention is maintained for a long period of time steadily and continuously, it transforms into Dhyana automatically. When the non wavering/varying singular focal attention flows, shining brilliantly, then the feel of this ‘I’ fades out. When the feel of the ‘I’ fades out, absorption is felt. This is
Samadhi. Here, the focus of attention gets saturated. If the focus of attention is enhanced, time-wise, it transforms itself into dhyana (meditation). Similarly, if the same
focus of attention is prolonged time-wise, length-wise, and width-wise, it transforms into absolute absorption.