Herland by Charlotte Perkins Gilman

We were standing on a narrow, irregular, all too slanting little ledge, and should doubtless have ignominiously slipped off and broken our rash necks but for the vine. This was a thick-leaved, wide-spreading thing, a little like Amphelopsis.

"It's not QUITE vertical here, you see," said Terry, full of pride and enthusiasm. "This thing never would hold our direct weight, but I think if we sort of slide down on it, one at a time, sticking in with hands and feet, we'll reach that next ledge alive."