From Comet in Moominland by Tove Jansson:
“But how do you know that the Observatory is on that peak especially?” asked Sniff, craning his neck to see the top, but without success as it was hidden in the clouds.
“Well,” answered Snufkin, “you only have to look at the ground just here. It’s covered with cigarette ends which have obviously been thrown out of the windows by those absent-minded scientists up there.”