What are three superstitions in Huckleberry Finn?

Could you elaborate on the superstitions mentioned in Mark Twain's classic novel, Huckleberry Finn? Specifically, what are three key superstitions that play a role in the story and how do they impact the plot or the characters' development? It would be intriguing to explore how these superstitions reflect the societal beliefs and folklore of the time period depicted in the novel.