Description, on pp.77-78, of the dirt-filled copper kettle connected to a drainpipe, in the cellar of the royal palace, through which the evil fairy Malavola, taking the form of a mole, sneaks into the christening of the princess, in "The Princess and the Hedge Pig", pp.73-94 of E. Nesbit's The Magic World, 1912 (Puffin Books, 1988).
... for of course there was a copper in one of the palace cellars, as there always is in cellars in the North Country.
Now this copper had been a great trial to the decorators. If there is anything you don't like about your house, you can either try to conceal it, or `make a feature of it'. And as concealment of the copper was impossible, it was decided to `make it a feature' by covering it with green moss and planting a tree in it. ...
Nesbit's children's stories are full of interesting and often "subversive" ideas, and striking word-play, and I recommend them (despite occasional anti-Semitic stereotyping of some minor characters in stories set in the "real" world).