As mentioned in the previous post, there are many superstitions about Boo Radley, most of which exist in the minds of children.
According to "the neighborhood scold," Miss Stephanie Crawford, Boo is a voyeur:
Miss Stephanie Crawford said she woke up in the middle of the night one time and saw him looking straight through the window at her… said his head was like a skull lookin' at her. (Ch. 1)
Town gossip attributes to Arthur Radley the "stealthy small crimes committed in Maycomb," and if people's flowers freeze, it is said that Boo's breath is responsible.
Another superstition about Boo attributes bizarre behavior to him:
Boo was about six-and-a-half feet tall, judging from his tracks; he dined on raw squirrels and any cats he could catch, that's why his hands were bloodstained—if you ate an animal raw, you could never wash the blood off. (Ch. 1)
While most of the superstitious beliefs are attached to Boo Radley, Mr. Avery holds a superstitious belief that leads him to accuse Jem and Scout. When there is a rare snowfall in Maycomb, which is in southern Alabama, Mr. Avery blames the weather on Jem and Scout. As the children stand on the sidewalk in front of Miss Maudie's house, they are accosted by Mr. Avery, whose face is pink.
"See what you've done?" he said. "Hasn't snowed in Maycomb since Appomattox." (Ch.8)
He tells Jem and Scout that bad children like themselves have caused this snow. Angrily, Mr. Avery asserts that in the past, events such as this rare snowfall have occurred "when children disobeyed their parents, smoked cigarettes and made war on each other" (Ch. 8).
After hearing this, whether or not it is intentional, the children build a snowman that resembles Mr. Avery. But, of course, the ever-observant Atticus perceives the resemblance to Mr. Avery, and he scolds the children, suspecting they built it in retaliation. He makes the children alter the snowman's appearance.
There are many superstitions surrounding the Radley family, and virtually all of them are based on Boo. If azaleas froze, it was because Boo breathed on them. You didn't eat from the Radley pecan tree because Boo had poisoned the nuts.
A Negro would not pass the Radley place at night, he would cut across to the sidewalk opposite and whistle as he walked. (Chapter 1, page 9)
One of the items left by Boo in the secret knothole of the Radley oak was a pair of pennies. Upon closer inspection, Jem determined that they were old--from 1900 and 1906--and that they were
"... Indian-heads--well, they come from the Indians. They're real strong magic, they make you have good luck... things like long life 'n' good health, 'n' passin' six-weeks tests." (Chapter 4, page 55)
I'm not sure where Jem got his information about the pennies' magical powers, but he probably picked up the information from other school kids. Historically, there is no magic or superstitions associated with the Indian-head penny.