The "Slip Chair" looks too unstable to sit in, but isn't

The folks at Snarkitecture collaborated with the Portuguese design firm UVA to create the "Slip Chair", which looks like it's tipping over, but is safe to sit in.

Or so they say! Me, I'd like to see a picture of someone actually sitting in one. But for now I'll take their word, as they write on the UVA site ....

Slip Chair is a wooden chair that appears to be sinking into the ground. As it may seem unusable at first, the wooden frame is even out with a tapered stone and a functional surface for sitting is provided. The apparently opposed elements of the chair are counterbalanced through the monolithic volume of the stone. The chair revolves upon two axes and the suggested unsteadiness of the sliding forms conceals the complete stability of Slip.

(Picture via UVA)