Cannery Row, like every place else, is not superstitious but will not walk under a ladder or open an umbrella in the house. Doc was a pure scientist and incapable of superstition and yet when he came in late one night and found a line of white flowers across the doorsill he had a bad time of it. But most people in Cannery Row simply do not believe in such things and then live by them.
—John Steinbeck, Cannery Row, chapter 25
A quick search doesn’t turn up anything relating to white flowers across the doorsill and their insalubrious nature. Any suggestions?