havent watched it yet but i think this is it
spoiler: heres a theory under the comments for how the trick was done. watch the trick first before u read it tho imo.
Great trick. He's using two very thin but strong ropes to suspend him. The rings are an illusion and they never over him. He is oriented sideways in the box because the two ropes suspending him are pushed down between the lid and the box itself. The girl on top of the box walks between the ropes. Copperfield is very cool for coming up with this trick. I would love to have some of this rope. I got all my info off off the web. I am not smart enough to figure this out on my own.