Have you seen a Buddha sitting on a lotus? You know, sits on the butt with legs in a intertwined crossing such that the right foot rests on the left thigh and the left foot rests on the right thigh, with soles facing up. Such a sitting position is called the lotus position. It is also one of the most basic posture of yoga, and does take some flexibility and getting used to.
If a man assumes a lotus posture and a woman sits on the penis of the man, then that's the lotus sex position. That'd be the ultimate zen of copulation.