Vrikshasana - The Tree
Sastri: True. The tree represents the spinal column. The leaves are threefold. They represent the Ida, Pingala and Sushumna Nadis, which are the regions for the activity of the moon, the sun and fire respectively, or which may be thought of as the three eyes of Shiva. The climbing of the tree is meant to represent the ascension of the Kundalini Shakti, the serpentine power, from the lowest nerve centre called the Muladhara to the Ajna Chakra. That is the work of the Yogi. Shivratri by Sri Swami Sivananda
Vriksh वृक्ष : tree.
Vrikshasana is mentioned and described in the Gheranda Samhita, a 15th century Hatha-yoga text.
Upon exhalation, switch the weight on the right leg. Bend the left leg and bring the sole of the left foot on the proximal and medial side of the right leg. The tip of the left foot points downwards and the heel is slightly anterior compared to the tip of the foot.
Note: Variation: the left leg can also be placed on the right thigh in half lotus.
The eyes fix a virtual or real point: The ocular fixation acts as a real anchor. The supporting foot and leg must be as relaxed as possible. There must be a feeling of rooting.
The trunk must be as straight as possible, and the thigh of the lifted leg must be rotated outward without tilting the hips.
Mula Bandha is active, and one must focus on the link between the root and the fontanel.
Breathing must be as subtle as possible, almost trickling peacefully.
Advanced Balance: once stable in the position, as the body learns the archetype, one eye and then both can be closed.
First, far from pacifying the mind, this posture brings to an increased mental activity. With focus, all diversions are brushed away and the focus remains on the point of ocular fixation and on the balance.
This posture brings back to the indifference towards the immediate surrounding. It induces the ability to step back and brings forth a pacification of the mind. It involves the heart center.