Would something like a Stress Cube even be eligible for a patent? I don't see the technological novelty to be honest. Maybe I'm misunderstanding how patents work.
Considering that the magic 8-ball has a patient, why not? (Granted it is actually an interesting patent since it solved the problem of air bubbles obscuring the answers on the answer die)
https://www.google.com/patents/US3119621
It'd probably be eligible for a design patent or trade dress protection.