tin foil

There's a bit in the Maira Kalman book, THE PRINCIPLES OF UNCERTAINTY, about her demented aunt who tried to pay for a sandwich (I think...) with packets of sweet and low. Interestingly enough this is a common form of currency amongst the nursing home "memory unit" crowd. Which led me to start thinking about how tin foil is a common item used by psychotic people to defend themselves against the entities their delusions lead them to fear. You know, like aliens, microwave radiation, sprocketheads...(Oh forget the sprockethead reference. Everyone knows the only defense against them is a variable speed power drill, preferably cordless with a fully charged battery. )
They put tin foil on their windows, on their heads, in their pockets, anywhere the foe might seep in...
That led me to think, "what did stone age paranoids use to defend themselves? What came before tin foil?"