I like this Sam Pottsesque shirt from Qwantz. It would be useful for when it all goes down.
But there is a basic problem:
There should be instructions for how to make a mirror at the top and then everything else below it printed in reverse, Memento-stizz.
This way, I won’t have to take my shirt off all the time to read it and I can thereby avoid frightening the old-timey people with my sixpack.
All that aside, a great effort and I can't wait to see cowpox up close.
(also with a backwards shirt, you could also potentially take credit for backwards writing before da Vinci does. TAKE THE CREDIT)