The word vajroli is derived from the word vajra which has various meanings and implications. In the context of vajroli mudra, vajra can be regarded as the name of a nerve which connects the sexual organs with the brain. It is also a psychic pathway that is associated with the sushumna pathway5. This pathway is directly connected with the unleashing of powerful psychic forces.
There are two types of vajroli mudra – one is concerned with maithuna (sexual intercourse under prescribed conditions) and the other is a simple raja yoga form. It is the latter that is utilized in kriya yoga.
The technique is as follows: Sit in any comfortable position. Place the hands on the knees and relax the whole body. Try to draw the sexual organs upwards by pulling and tensing the sexual organ and lower abdomen. This contraction is similar to that which is made when one has the urge to urinate, but has to retain the urine for some time. The testes in men and the vagina in women, should move slightly due to the contraction. This is the simple form of vajroli mudra.
Its purpose is to convert retas (sexual energy) into ojas (highly refined pranic or psychic energy). This process is called urdhva retas the sublimation of sexual energy. Prana is the essence of both ojas and retas; vajroli helps to bring about sublimation of the grosser retas into the more refined ojas.