^ James Mallinson, "Sāktism and Hathayoga," 28 June 2012.
Archived 16 June 2013 at the Wayback Machine [accessed 19 September 2013] pgs. 2 "In its earliest definition, in Pundarīka's eleventh-century Vimalaprabhā commentary on the Kālacakratantra, hathayoga is said to bring about the "unchanging moment" (aksaraksana) "through the practice of nāda by forcefully making the breath enter the central channel and through restraining the bindu of the bodhicitta in the vajra of the lotus of wisdom". While the means employed are not specified, the ends, in particular restraining bindu, semen, and making the breath enter the central channel, are similar to those mentioned in the earliest descriptions of the practices of hathayoga, to which I now turn."
Similarly, Brahma sutras – the foundational text of the Vedanta school of Hinduism, discusses yoga in its sutra 2.1.3, 2.1.223 and others. Brahma sutras are estimated to have been complete in the surviving form sometime between 450 BCE to 200 CE, and its sutras assert that yoga is a means to gain "subtlety of body" and other powers. The Nyaya sutras – the foundational text of the Nyaya school, variously estimated to have been composed between the 6th-century BCE and 2nd-century CE, discusses yoga in sutras 4.2.38–50. This ancient text of the Nyaya school includes a discussion of yogic ethics, dhyana (meditation), samadhi, and among other things remarks that debate and philosophy is a form of yoga.
Core: Yes. There are yoga poses to target just about every core muscle. Want to tighten those love handles? Then prop yourself up on one arm and do a side plank. To really burn out the middle of your abs, you can do boat pose, in which you balance on your "sit bones" (the bony prominences at the base of your pelvic bones) and hold your legs up in the air.