The word ‘yoga’ is very old and occurs in early Upanishads like the Katha and the Svetasvatara as well as in Mahabharata but it was Patañjali who attempted for the first time to offer a complete system in his Yoga-Sutra. Authorities differ as regards the exact time of the composition of the Yoga-Sutra. According to some it was written in the second century b.c., whereas others believe that it was composed as late as the fourth century a.d.