I found one of these at one of the big camping and outdoors mega stores the other day. About a hundred bucks and only 9.1 ounces. If your looking ultra, ultra, ultra light. This might be it. I've never used one but reading this page reminded me of this thing.
Their website.

http://www.klymit.com/index.php/prod...riaxframe.html

Smallest I've ever seen. No good if you sleep on your side.