Huck has experiences he interprets as bad omens several times through the course of the story. In the first chapter, he brushes a spider off his shoulder and it lands in a candle flame and burns - a sure sign of bad luck.
In chapter 10, Huck reminds Jim about the snake-skin Huck had found and touched. Jim insisted that action would bring terrible bad luck, which Huck discounted since the next day they collected all kinds of valuable items from the house floating down the river. Three days after that evening, Jim was bitten by the rattlesnake Huck put on his blanket as a joke. Huck truly became a believer in bad omens as a result of this incident.
I made up my mind I wouldn't ever take aholt of a snake-skin again with my hands, now that I see what had come of it. Jim...said that handling a snake-skin was such awful bad luck that maybe we hadn't got to the end of it yet.