On a plinth are three big pillars with a bench in between. Your assistant (or you yourself) goes and sits on the bench. Slowly but surely she rises, losing all contact with the seat. She begins to hover in mid-air. Take away two of the three pillars. Your assistant continues to ascend. Next, take away the bench as well, so that your audience can verify the gaping void beneath your assistant even better. She rises the full height of the remaining pillar. After a few seconds of having her head in the clouds, she floats just as gracefully back down again. Slide the bench back underneath in time so that she can recover from her ordeal and gets her wits back. A splendid illusion which simply exudes class. Quite straightforward - both for the magician and his assistant.