This is the first stage of a pose, where both legs are dropped to the side, either side, sharply to each side, so that u are actually hanging on from one of your wrists! The last time I attempted it, to dissatisfaction and imperfection, was at the ashram, under Janaki's guidance, as she led an evening class for the advanced yoga teachers' batch. I kept trying it at the ashram, and felt maha pleased, till I took a photo of myself executing it and felt how far off the mark I was off!!:)
In this pose, the depth is reached by keeping on lowering your legs towards the floor. Plus sharpening the sideways twist. That calls for tremendous practice... And strength.
PREPARING FOR THIS POSE
To prepare for this pose: You must be able to drop comfortably from the shoulderstand into the bridge. And walk in the plough, bridge chain sequence (mala). Main strength is from the wrist. But also, lightening up is important. That happens on its own, when the muscles power up, become strong. Mostly being light comes from strength, an interesting oxymoron that also defines pure yoga for me:)