the yoga scholar norman sjoman is critical of the book's perfunctory treatment of both academic requirements and yogic practices other than asanas. he comments that krishnamacharya's list of sources "reveals his relation to tradition", but is "a padded academic bibliography with works referred to that have nothing to do with the tradition he is teaching in". the list includes for instance the well-known hatha yoga texts, the "hatha yoga pradipika", the "gheranda samhita" and the "sritattvanidhi" as well as the yoga upanishads. sjoman gives as an example the recommendations for "vajroli mudra" which call for "a glass rod to be inserted into the urethra [of the penis] an inch at a time. his recommendations show that he has most certainly not experimented with this himself in the manner he recommends."