PURPORT

It appears from this statement that Dhruva Maharaja had already been instructed how to practice the eightfold yoga system, which is known as astaṅga-yoga. This system is explained in our Bhagavad-gita As It Is, in the chapter entitled, "Saṅkhya-yoga," pages 319-322. It is understood that in astaṅga-yoga one practices settling the mind and then concentrating it on the form of Lord Visnu, as will be described in the following verses. It is clearly stated here that astaṅga-yoga is not a bodily gymnastic exercise, but a practice to concentrate the mind on the form of Visnu. Before sitting on his asana, which is also described in Bhagavad-gita, one has to cleanse himself very nicely in clear or sacred water thrice daily. The water of the Yamuna is naturally very clear and pure, and thus if anyone bathes there three times, undoubtedly he will be very greatly purified externally. Narada Muni, therefore, instructed Dhruva Maharaja to go to the bank of the Yamuna and thus become externally purified. This is part of the gradual process of practicing mystic yoga.