“There!” said Ford, shooting out his arm; “there, behind that sofa!”
Arthur looked. Much to his surprise, there was a velvet paisley-covered Chesterfield sofa in the field in front of them. He boggled intelligently at it. Shrewd questions sprang into his mind.
“Why,” he said, “is there a sofa in that field?”
“I told you!” shouted Ford, leaping to his feet. “Eddies in the space-time continuum!”
“And this is his sofa, is it?” asked Arthur, struggling to his feet and, he hoped, though not very optimistically, to his senses.
“Arthur!” Ford shouted at him, “that sofa is there because of the space-time instability I’ve been trying to get your terminally softened brain to come to grips with. It’s been washed up out of the continuum, it’s space-time jetsam, it doesn’t matter what it is, we’ve got to catch it, it’s our only way out of here!”
He scrambled rapidly down the rocky outcrop and made off across the field.
“Catch it?” muttered Arthur, then frowned in bemusement as he saw that the Chesterfield was lazily bobbing and wafting away across the grass.
With a wild whoop of utterly unexpected delight he leaped down the rock and plunged off in hectic pursuit of Ford Prefect and the irrational piece of furniture.
from Life, the Universe, and Everything by Douglas Adams; quote via a pocketful of change
On eddies in the space-time continuum