“Now she took the sword back into her hand and knelt on the rim of the invisible blackness below. She had gone this path once before and once only, and never thought to find any necessity in life strong enough to drive her down again. The way was the strangest she had ever known. There was, she thought, no such passage in all the world save here. It had not been built for human feet to travel. It had not been built for feet at all. It was a narrow, polished shaft that cork-screwed round and round. A snake might have slipped in it and gone shooting down, round and round in dizzy circles—but no snake on earth was big enough to fill that shaft. No human travelers had worn the sides of the spiral so smooth, and she did not care to speculate on what creatures had polished it so, through what ages of passage.”

Source: The Memory Keeper's Daughter

Black God's Kiss (1934)
Context: She half expected, despite her brave words, to come out upon the storied and familiar red-hot pave of hell, and this pleasant, starlit land surprised her and made her wary. The things that built the tunnel could not have been human. She had no right to expect men here. She was a little stunned by finding open sky so far underground, though she was intelligent enough to realize that however she had come, she was not underground now.

For My Country's Freedom, Cap 5 "Indomitable"

Mary in Ch. 34 : There is Now
His Dark Materials, The Amber Spyglass (2000)

Source: Jack Faust (1997), Chapter 17, “The Agent” (p. 304)

Very Good, Jeeves (1930)
Source: Carry on, Jeeves

Ch 11 - p.217
Novels, Midwinter Break (2017)

Source: Way Station (1963), Ch. 16
Context: He had acted on an impulse, with no thought at all. The girl had asked protection and here she had protection, here nothing in the world ever could get at her. But she was a human being and no human being, other than himself, should have ever crossed the threshold.
But it was done and there was no way to change it. Once across the threshold, there was no way to change it.