HathaYoga Pradipika begins with: “Yoga was first known to Gorakhnath and Matsendranath and Swatmaram Yogi knew it by the grace of these two.”
The Gorakh-Bodh (“Illumination of Gorakh) is an obscure ancient Hindi text, by Nath Yogis, written as an intense dialogue between Gorakhnath and his Teacher, Matsendranath. Both of these two givers of the great knowledge of yoga were considered to be immortal.
Ffounder of Natha’s, Matsyendranatha or Macchandanatha, left several sacred texts belonging to this
mystical school. He believed to be the author of the Kaulajnananirnaya and supposetly wrote the Yogavisaya under the pen-namet Minanatha. There is no certainty of his dates; he may have lived between the eighth and tenth centuries.
His disciple, Goraksanatha, is widely known and respected in India as a great siddha. He wrote the Siddhasiddhantapaddhati, the Amaraughaprabodha (“Awakening R-vealing Immortality”). Another work by Gorakshanath, The Amaraughasasana, “Immortal Plow,” describes the methods to conquer time and death and enables the yogin to become aware of nonduality and quickly reach the efficience, called amaraughasiddhi.
Belonging to Sivagotra, the Natha are following Shiva, regarding Him as pure Consciousness which enjoys quietude
and eternity, whereas Sakti, his energy, is the source of change and of the varied experiences related to it.
For the Nathas an achievement of liberation in life is a main goal. Outer religious practices and scriptural knowledge considered to be of lesser value. Their only emphasis is on a direct way, as short as possible, a tread through which the mystic discovers within himself, right in his own body an experience of the energy of the Universe.
G Through which centre can one make one’s body immortal? Through which centre can one attain to the Unknowable dam (Agochar bandh)? Through which centre can the Hamsa be liberated (Hans nirodh)? Through which centre can the mind be instructed? Which centre gives pleasure? Which centre brings on the Samadhi? 
M The anus (Mula) centre; the penis (Guda) centre; the navel (Nabhi) centre; the heart centre; the throat centre and the head (Nilata) centre. He who knows the meaning of these six chakras, he is the Cause, he the Deva. 
Sri Shailendra Sharma:
Don’t you think it is a perfect description of the siddhasana in Kriya Yoga?
Let’s take a look: Aghochar bandha or mulabandha is taking place, penis chakra is controlled in the process, the fire is moving up, Prana and Apana are rising through the heart, throat and head centers and the accomplished mastery of all these components might lead practitioner to immortality.
Deeper understanding of the process and control of the body will develop with persistent and regular practice. And finally yogi will develop an ability to control and move energy, which takes some patience and truly artistic creativity .
Through which centre can one make one’s body immortal?
Way to obtain immortality with the means of the yogic art are: mahamurdra, mahavedha, mahabandha,mullbandha, yddiana bandha, jalandhara bandha and khechari.
Babaji is an immortal giver of the Kriya yoga – and some hints on immortality is to be discovered in this very teaching of art of kriya.
The anus (Mula) centre
Agochar bandh (invisible bandh) or mulbandh is most powerful and most vital marm, the center of nervous system, directly connected with the mind.
In the human embrio this center is forming ahead of all other vital centers and that’s why it is connected with immortality.
The penis (Guda)
A tool for creation, penis is a giver of the seed, supplying the substance of new life. In yoga wise usage of sex center can prolong life.. It is a hint for brahmachari, who can prolong it’s own life by reversing the flow of the energy, reverting it’s outward current to inward.
Remaining unseen, this center creates life
Together with Mula, Agochar bandh Guda center is an unknowable because the doer will never see the very moment of creation of the new life by his own sperm.
Through which centre can the Hansa be liberated (Hans nirodh)?
Hansa is a seed mantra of your breath and if flies from the Heart Center.
When we are breathing out, the sound “HUM” arises naturally. Sound of inhaling comes as a”SAH”. Every Indian knows that the soul, Jiva is Hams, identified by the sound of constant breath in all living creatures.
Paramatma, creator of Ishvara is called Parahams – The Hams of the hams, Swan of the swans, The Jiva of all jivas…It is also known by the name of God- for the lack of better terms.
Through which center can the mind be instructed?
– the throat centre and the head (Nilata) centre.
Instruction to the mind is given via combination of yogic breath technique and khechari mudra.
Throat center consolidates myriads of nerves and nadhis, running down to the lower parts and organs of the body, connecting upper and lower.
Vital air and food are supplied through this center and it is directly affecting nearest heart center, which is refining energy, received via the throat.
Mastered control of the throat center gives full control over all functions of the body. That’s why jalandhara bandha is considered to be one of the most important bandhas in yoga.
Nilata is an inner center inside of the front part of the scull. This empty spot is located right behind inner nasal passages – tongue enters this space during khechari mudra. Mind resides in the scull as a supreme ruler of the body, living in the castle and receiving all the energy from the Heart and Vauy – they are serving him like devoted and loyal vassals, worriers and servants, supporting his mighty power.
Which center gives pleasure? Which center brings on the Samadhi?
He who knows the meaning of these six chakras, he is the Cause, he the Deva.
Only a yogi, whose energy is passing through the spinal cord knows all six chacras. Such yogi is a master of Sushumna. He is a cause of his own existence or self destruction –and it is a final achievement of yogic practice of awakening the Kundalini. Passing through the spinal fluid, energy is creating all the chacras and activating them at the same time. Only such yogi will know the chakras.
Gaining Control of Mula and Vayu, obtaining knowledge of Lalat and Nilat will enables practitioner to enter his own consciousness inside of Sushumna.
Only knowledge of all six chakras inside the Sushumna will lead to the experience of the Samadhi.
This knowledge is the key to the doors of Samadhi, behind which yogi will find the the greatest of pleasures..
He is a Yogi who controls (sadhita) the mind and the vital air (pavana); he is not stained by evil. He is not seized of merit. 
Interview and composing text by Ilya Khanykov.