Occasionally a young child or two visits our house. We have a few appropriate toys with which to amuse them, and their parents usually bring a some favorites as well. But when the kids get bored, we bring out the coasters.
We have a little round lacquer wood box, solid yellow, containing a few round lacquered wood coasters, just wide enough to hold a glass. These were very popular Japanese imports in the Sixties. They look nice, feel smooth, and click nicely when banged together. And then we have similar red and blue ones.
Most young kids will play with these coasters ten times longer than with a toy, even more than an hour! They stack them, drop them, pattern them, put them away, take them out, and somehow remain spellbound. What an extraordinary toy, and how simple!