Parivritta Surya Yantrasana | 4 minutes | Level 2

Parivritta Surya Yantrasana is Compass (or Sundial) Pose: parivritta means revolved, surya means sun and yantra means instrument. It's a seated hip-opening posture, and is not one you come across often so is fun to put into the seated section of your practice for variety. It opens the hips and shoulders, stretches the hamstrings and spinal column, and opens the groin and the sides of the torso and lungs.

It's intemediate to advanced. Don't try it unless your hamstrings are already quite flexible, otherwise it's a struggle (practise Paschimottasana and Uttanasana regularly to develop that flexibility). This video is a short sequence of postures you can do to warm up and prepare for it: 
Siddhasana with a forward fold and Badha Konasana to open the hips (it's nice to stay in these for some time, breathe deeply and let the hips slowly open more deeply);
Paschimottanasana to stretch the hamstrings (keep it active – the legs engaged and spine extending forward – rather than passive);
Ardha Matseyendrasana – a spinal rotation.
(Janu Sirsasana would also be good, as it opens the hip and stretches the hamstrings at the same time.)

To get into this posture, draw the left heel into the groin and let the knee fall out to the side. Use your hands to lift the right knee over the right shoulder (or as close as possible) and place the right hand on the ground away from the body, level with the hip. The left hand is reaching across and holding the outside of the right foot. Keeping this hand and foot connected, push the right sole up to the sky as you take the left arm over and behind the head.

Once in the posture, keep both buttocks on the ground while lifting the lower spine and lengthening up through the entire spine (don't let your back slump). Lift the lower ribcage away from the hips. Firm the right hand into the ground and keep rotating the right shoulder outward. Keep pushing the raised foot into the hand. Don't crank the neck to look up: turn it slowly.

Breathe fully and evenly into the open side of the torso and belly. With each inhale, lengthen the spine. With each exhale, relax your shoulders down while pushing the sole away, feeling the extension through the leg and your breath deeply filling the left side of the lungs and abdomen. Stay here for 20-30 seconds as long as it's comfortable, you are breathing fully, not straining and your mind is calm.

When exiting, take care of your neck and first turn the head slowly to look down, then unwind yourself out of the posture. Come on to your knees and rest in Balasana. 

Don't do this if you have any hip, groin, knee, hamstring, lower back or shoulder issues, or if you are not warmed up or don't yet have sufficient flexibility in the legs and hips.