I saw them in my dream, that they went on in this their solitary ground, till they came to a place at which a man is apt to lose his way. Now, though when it was light their guide could well enough tell how to miss those ways that led wrong, yet in the dark he was put to a stand. But he had in his pocket a map of all ways leading to or from the Celestial City; wherefore he struck a light (for he never goes without his tinder-box also), and takes a view of his book or map, which bids him to be careful in that place to turn to the right hand. And had he not been careful here to look in his map, they had all, in probability, been smothered in the mud; for just a little before them, and that at the end of the cleanest way too, was a pit, none knows how deep, full of nothing but mud, there made on purpose to destroy the pilgrims in.
John Bunyan, Pilgrim's Progress.