Hourglass

Hourglasses are a cool and ancient timekeeping technology.

Now, I posit that they developed when someone held a handfull of sand and let it drain through the bottom of their fist... the curled little finger.

So, I'd like an hourglass in which each bulb is a fist shaped so it appears the sand is draining through it in this (with sand filling the shape it to make it clear. The exact proportions may need to be tuned, as well as the exact shapes so that sand is never trapped in the wrong bulb.

See also Wikipedia:Hourglass