Vajrasana
In Sanskrit, Vajra means "thunderbolt" or "diamond like" and Asana means "pose" or "seat." This Asana translates to Thunderbolt Pose or Diamond Pose.
This practice is one of the thirty two Asanas described in the Gheranda Samhita as being helpful for humanity. This Asana is a basic seated pose that does require the knees to be flexible but is a pose that most people can preform even after a meal which is unlike most poses.
Practice
Kneel on the mat with the knees close together and sitting on the heels.
Bring the big toes together and separate the heels.
Lower the buttocks onto the inside surface of the feet with the heels touching the sides of the hips.
Place the hands on the knees, palms down.
The back and head should be straight but not tense.
Close the eyes, relax the arms and the whole body.
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.