What is the lotus effect?

WHEN YOU FIND YOURSELF WATCHING the clock on the wall of a dentist's waiting room, you can always pass a bit of time with a rummage through the bowl of fragrant botanical wonders next to the leaflets about expensive cosmetic work. 

Interesting things turn up in a pot pourri. Among the dried leaves, flowers, cones, shavings and bark you might well find a distinctive, holey disk on a stick that could be a showerhead in a Hobbit's bathroom.