On Page 320 of my copy of PR, Cayce confronts a fence that may be electrified -- "She extends her finger. Takes a breath. Taps the chain link as lightly, as quickly as she can. No shock..."
If you ever need to do this, you must touch the wire with the BACK of your hand -- old electrician's trick for testing live wires. If there is a shock, the muscle reflex will jerk your hand BACKWARDS, off the wire. If you "tap", and there's a shock, the reflex will jerk your hand towards the wire, and you will be unable to withdraw it and you will fry. Here's something from the net:
"When the time comes to actually make contact with the conductor(s) of a supposedly dead power system, do so first with the back of one hand, so that if a shock should occur, the muscle reaction will pull the fingers away from the conductor.
The guy who taught me this (30 years ago) said that firemen are trained to enter a burning building with the palms of their hands facing them, for just this reason -- if they run into a live wire, the reflex will jerk their hands away.
BTW, I have to say that Cayce's escape from that "prison" has to be the single most unlikely event I've ever read in fiction -- would she just be left unattended like that? But never mind, real life is much stranger than any fiction.