I have managed to do it twice; foot only both times. Once, floor of the attic was decked with OSB and well insulated, however, right at the opening (of all places) the insulation went over the top of the OSB, the client asked me something about the same time my foot went right through the insulation to where the OSB SHOULD HAVE BEEN and right on through.

Second time, I was carefully walking on the chords of the rafters and reached for the next purlin, which apparently had never been nailed and momentum is not always a good thing, by the time I caught my balance, my foot was already through.