TSA, meet Archimedes. He lived over 2,000 years ago and figured out how to calculate the volume of a object by measuring its displacement. If you actually believe that 3 oz is a magical high-danger threshold, please consider adding a delightful, hallucinatory element of science to your pseudoscience by putting an Archimedes tank at the checkpoint. It would be a lovely counterpoint to your other scientific tests, such as the ducking stool and the spirit-rattles.
Snow globes? TSA will likely just say 'no' (via MeFi)
"Snow globes are not permitted to be carried through security checkpoints," said Transportation Security Administration spokesman Dwayne Baird.
The reason is that the globes contain liquids, and TSA rules say that only liquids, gels or aerosols in containers of three ounces or less are allowed through security in carry-on bags...
"I would think they would just say 'no,' because they can't really determine how many ounces are in there," Baird said.