I've been trying to do this for a long, long time. I have two legs, but I can only bend one of them to land, and for you Capoiera kids out there, I'd be landing in 'negativa' with one leg outstretched. I'm not sure I have the arm-strength for it though. I can get my legs up over my head really easily, but the springing 'wave-like' action is quite difficult. Any tips?
The secret is in the legs, let their weight and momentum do the work, throw the legs at a 45ยบ angle, tuck the leg(s) under and sit up. The hard part will be controlling the landing if you over commit you fall forward. This is a real "learn about your body" stunt. Its mechanics are slightly different for everyone so you just have to keep trying different things till it happens.