As long as it is "properly packaged, labeled and declared," one may take Victorian philosopher Jeremy Bentham's mummified head onto your flight. The TSA added that travelers may simply snap a picture and tweet it to @AskTSA if they are in any doubt about the flight-legality of any desiccated human remains with which they wish to fly.
Jeremy Bentham was an English philosopher who died in 1832, but not before requesting that a physician friend publicly dissect him and then preserve him as an "auto-icon." This was achieved by clothing his skeleton in one of his suits, sitting it on a chair and displaying it inside a wood cabinet. Originally, Bentham's preserved head was supposed to be attached to the auto-icon, but it turned out to be pretty gross, so a wax replica was made instead.
Bentham was into utilitarianism, social reforms and animal rights. The auto-icon is on display at the University College of London. If you can't visit him in person, you can still check out the scenery thanks to a webcam mounted on his cabinet.