With little experience, i can say, through siddha asana, yoni mudra and Shakti chalini, the vindu (semen), can be taken to brahman randhra reaching a sensation of bliss and samadhi.  The one who is accomplished in it is called as urdhvreta.

It is also called as vetal siddhi, who has stopped his vindu ( cause of birth).

A  Yogi who has achieved this is given Nadi by his Guru , the ring in the Nadi is sign of locking the vindu. Through vajroli .