https://marco.org/2010/01/27/i-made-a-life-size-cardboard-ipad-and-some-paper
I made a life-size cardboard iPad and some paper sketch templates for Instapaper interface design.
One surprise when fake-“using” the cardboard iPad: I can use the whole keyboard with just my thumbs, holding the iPad in the air. And I can use it surprisingly quickly. My assumptions about input limitations may have been premature.