Vasisthasana ~ Side Plank
Vasistha was a sage who taught King Ram, one of the avatars of Vishnu. Ram's role on earth was to restore righteousness which had become corrupted by negative influences. Ram's father, King Dasharatha, became concerned for his son after he returned from travels and seemed quite disillusioned at the state of the world. He asked Vasistha to help out. The sage was pleased to hear of the circumstances of Ram's state of mind because he felt this was a precursor to the spiritual path. He went to Ram himself.Ram was skeptical that Vasistha would be able to lift his spirits. He felt that life had lost its luster and was quite depressed. Vasistha explained what Ram needed to regain his vision for this life and told him that he would guide him.Many need to hit rock bottom before they can move forward, just as Ram did. The soul that is interested in transformation is suited to spiritual pursuits. We begin to realize that we can be content with the way things are while making change that better serves our spiritual pursuits. This subtle difference needs to be understood as we progress down the path of yoga.To take the pose Vasisthasana, start in a plank pose as shown here:
Next, you will turn over onto your right hand and the pinky toe side of the right foot. Ensure that the shoulder blades are firmly rooted onto the back and lift through the hips so that the entire body is staying in one straight line. You need to use your core to take this pose. The obliques along the side of the abs are going to work hard here. Imagine that you are lifting out of the shoulder of the balancing arm. You can look up at the top hand if that feels okay for your neck.
If you have trouble balancing, though, look down at the bottom hand. As in every arm balancing pose, make sure that you press firmly into the triad of the hand: 
There are variations to this pose if you find that your hips are dropping. In this version, the top foot comes forward and acts as a kick stand. The same cues for alignment as mentioned above still apply here:
Another variation is on the knee as shown here: