"Letters" and Words
A box of letters is an unfailing help to pass the time. A word will sometimes keep a player puzzling for hours, which is, of course, too long. "Pomegranate," "Orchestra," and "Scythe" are good examples of difficult words.
You can also take words and sentences seen on the journey, such as "Wait till the train stops," and "Pears' Soap," and see how many words they will make. A more difficult task is to make anagrams of advertisements. "Lipton's Teas," for instance, makes "Taste on, lips."