THE THIRD TRIAL OF ZENNESS

Acquire the 7 gallon vessel.
Make it full.

Pour the 7 gallon vessel into the 4 gallon vessel.

Acquire the 4 gallon vessel.
Make it empty.

Pour the contents of the 7 gallon vessel into the 4 gallon vessel.

Make full the 7 gallon vessel. Pour its contents into the 4 gallon vessel.

Place the 7 gallon vessel on the pedestal, for now it holds 6 gallons.

It is done.

The Cave, by Ron Gilbert & Double Fine Productions