Trepanation Kit, late stone age.
I love this web site of ancient inventions! This one is especially intriguing:
Trepanation is a method of brain surgery whose origins can be traced to the Late Stone Age. Some remote societies still practice it today, and in some tribal cultures of East Africa it has survived as an integral part of traditional medicine. Doctors employed this invasive procedure to relieve distress caused by a variety of disturbances, including skull fractures, parasites, pressure, hydrocephaly, incurable headaches, and even evil spirits. Intricate and refined instruments aided prehistoric surgeons in the different methods of penetrating the skull, and sometimes in actually removing tissue from the brain. --Trepanation Kit, Worldwide, 2000 BCE by Dierdre Crane