Khechari Mudra
In Sanskrit, Khechari come from two root words Khe meaning "ether" or "space," Charya means "one who moves" and Mudra means "gesture." One translation is "transversing the ethereal regions." This practice is a Mana Mudra or head gesture practice and is described in the Hatha Yoga Pradipika, Gheranda Samhita as well as the Shiva Samhita.
This gesture is described in two other Yogic text, the Khecarividya where it is stated that this practice enables Kundalini to rise up from Muladhara. In the Bhattacharya describes this gesture as bestowing spiritual attainment and gives the practitioner the ability to overcome disease and death.
This gesture is also associated with Amrita, the nectar of life, which is secreted by the Bindu Chakra, a point on the posterior fontanel, which is consumed by Vishuddhi Chakra. Perfection of this practice allows the practitioner to stop the decent of Amrita into Vishuddha, overcoming hunger and thirst, while rejuvenating the body.
This practice should be incorporated with the Ujjayi Pranayama. At first you will feel almost immediate discomfort, but with practice you will find that you can perform this practice for longer periods of time. This is one of ten Mudra practices that are said to destroy old age and death as well as giving Divine wealth.
Practice
Roll the tongue upwards and backwards so that the bottom of the tongue comes in contact with the soft palate.
Stretch the tip of the tongue backwards as far as is comfortable.
Do not strain.
Preform Ujjayi Pranayama.
When you feel discomfort, release the practice for a second or so and then again repeat the tongue lock.
The six cleansing actions are intended to be the start of a Yoga practice in order to clean, strengthen, remove toxins and improve the flow of Prana through out the practitioner.
Yoga poses help to elongate and strengthen the muscles of the body as well as to calm the mind for the deeper spiritual practices of Yoga.
Breathing exercises are a great practice to remove carbon dioxide, increase lung capacity as well as being a good preparatory practice for the deepest spiritual practice of Yoga, Meditation.
The four body locks that makes up this practice give the practitioner the ability to hold or lock Prana in certain locations of the body. These practices also allow the practitioner to release blockages that may be holding the practitioner back.
The gestures in this practice include the whole body and are intended to awaken Prana, Chakras as well as Kundalini energy within the practitioner.
Meditation is the highest spiritual practice of Yoga which is why this practice is the most difficult practice to preform, but with correct knowledge and dedication, can be the most profound practice of Yoga.