De Selby's Toilet Brush

Affixed to the cistern of this otherwise unremarkable toilet is a quarter-scale fully functional model of the same, in which a toilet brush can be stored safely and hygienically. Flushing the miniature toilet efficiently cleans the brush that resides in its bowl.

Affixed to the cistern of the otherwise unremarkable quarter-scale fully functional toilet is a one-sixteenth scale model of the same, holding a tiny brush that can be used for cleaning the quarter-scale model.

Affixed to the cistern of the sixteenth-scale toilet is another, smaller toilet. It's of no use. It's just toilets all the way down.