(I would only boil it for about 1/2 hour.)
All of this is taken from the Jivaro (Shuar) people of the Peruvian and Ecuadoran regions of the Amazon rain forest, the only people in the last four hundred years to shrink heads*. (This is not the most interesting thing about them, either.)
One might ask, however, why one would wish to shrink a head. Well, when going on a raid, one might come back some useful tools, weapons or women. But the best prize of all is a male head. If the man beheaded has ever possessed an Arutam spirit, he will spawn a Muisak (Avenging soul) upon death. (He does not posses an Arutam spirit at the time of death--if he had, one would not be able to kill him. But all male Jivaro will acquire a Arutam sometime around their 7th year. Females rarely acquire Arutams, as Arutams cause you to have a great desire to kill. This would not be fitting in a female).
The Muisak, being an avenging spirit, is naturally out to kill the beheader. If the Muisak gets free, you are in big trouble. So, it is necessary to trap the Muisak in the head (the shrunken head is called a tsantsa). You shrink the head to preserve it, and you sew up all the holes so that the Muisak can't get out.
You then throw 'shrunken head parties' in which the Muisak is drained from the head. The first party happens right after you get home, and lasts two days. Nothing is done to drain the Muisak at this time, but it is a lot of fun.
The second party is a year or more later. It lasts for five days, and the whole neighborhood is invited, so it takes a while to get things ready. There's no hurry--the Muisak isn't going anywhere. But in the meantime the one who captured the head cannot go to war, go hunting (he'd better have a son to hunt for him), go fishing, eat meat, eat spicy foods, wear feathers, or sleep with women. Any of these activities might give the Muisak a chance to kill him.
When the second party takes place, the shrunken head is hung from a pole in the middle of the house, and everyone dances around it. The killer and two women will join hands, and draw power from the Muisak. This gives the three of them Arutam power, and it is often the females' only source of Arutam power.
If the household is up to it, a third party may be thrown one month after that. It would be the biggest of all, and would last six days. But parties are draining, and a household may not be able to afford it. If they can, another threesome drains the Muisak completely. If they cannot, no matter, the Muisak doesn't have enough strength left to do any damage.
The shrunken head is now a decoration and a status symbol, or it can be sold as a curiosity to some crazy American for a couple hundred dollars.
* AshleyCash points out that the
Nazis also shrunk heads; two of these were displayed in the
Buchenwald camp in order to intimidate the prisoners, and one was later used as evidence of Nazi atrocities in the
Nuremberg trials. Probably those viewing the evidence did not realize just how much trouble had gone into making these heads; these were not casual atrocities, but someone's grizily and carefully undertaken hobby.