By blocking all the channels (of perception) the prana- shakti moves slowly upwards (through the spinal column). At that time, feeling the sensation of an ant crawling in the body, one experiences the supreme bliss.
वहेर्विषस्य मध्ये तु चित्तं सुखमयं क्षिपेत् । केवलं वायुपूर्ण वा स्मरानन्देन युज्यते ॥ ६८ ॥
One should throw the blissful mind into the fire (manipura chakra) in the middle of that fibre-like lotus stalk (sushumna) or into that which is only full of air (anahata chakra). Then one is united with the remembrance of bliss.
By the union with shakti there is excitation and in the end, one is absorbed into shakti. That bliss (of union) which is said to be the nature of Brahman (ever-expanding consciousness), that bliss is (in reality) one's own self.
O Queen of Gods, the bliss of a woman is attained even in the absence of shakti. By fully remembering and absorbing the mind in the experience of kissing, hugging and embracing, the bliss swells.