See, back in the day, after the doctors finished lobotomising you with a stick and applying the leeches, they'd jam one of these on your noggin to see which of your humours was out of balance... or some such quackery. Our friends at Oobject.com have some more examples of stuff you don't want on your head.
19th century phrenology helmet
Strangley simple and baroque all at the same time
To keep your head still
Home Phrenology Device Crap science, but nonetheless superior to most installation art.
Mind-reading pinball helmet
Robot Phrenologist Reads your head bumps and prints out your character. I guess 99 per cent of the time it says gullible.
Stereotactic Head Frame For MRI scans
The Gill-Thomas-Cosman Relocatable Stereotactic Frame Another device to keep your head still
The Gnathograph A teeth measurement device worthy of a Terry Gilliam movie.
The Max Factor Beauty Micrometer A ridiculous device that combines the dubious claims of cosmetics with the outright quackery of phrenology.