Phisick.com is an online collection of antique medical instruments. In response to my query regarding which item is closest to a brain hammer, curator Laurie Slater writes:
www.phisick.com/a1mmazbr1.htm is a mid 19th century papier-mâché brain (a pretty one) and http://www.phisick.com/a1meh2.htm is a hammer, although one used more for percussion, like a primitive ultrasound - but not on the brain of course. I suppose if you were so inclined http://www.phisick.com/a8qfb1.htm might give an idea where to aim.
http://www.phisick.com/a2snstr1.htm is a brain drill which might have a similar effect to a brain hammer (if tidier). In fact it was a tool used to recover from ‘brain hammer’ type injuries. Drill three holes around a depressed skull fracture. Pass this http://www.phisick.com/a2snsg1.htm through them and saw out a triangle to releive the pressure on the cerebral cortex and patch up with a metal plate. Good as new!
Then I suppose there is this http://www.phisick.com/a1spr01.htm (hardly a blunt instrument I admit) which would proverbially hammer the brain via sensory overload into thinking of other things. I’m not sure if this would have been considered a cure for mental masturbation .. the affliction of many a philosopher. Present company excused of course!