Soup » posted to Soup and booklines
"They looked like tinkers, but there wasn't one among them, she knew, who could mend a kettle. What they did was sell invisible things. And after they'd sold what they had, they still had it. They sold what everyone needed but often didn't want. They sold the key to the universe to people who didn't even know it was locked."
On teachers from The Wee Free Men by Terry Pratchett ‎- Soup
Further description: "They went from village to village delivering short lessons on many subjects. They kept apart from other travelers and were quite mysterious in their ragged robes and strange square hats. They used long words, like 'corrugated iron.' They lived rough lives, surviving on what food they could earn from giving lessons to anyone who would listen. When no one would listen, they lived on baked hedgehog. They went to sleep under the stars, which the math teachers would count, the astronomy teachers would measure, and the literature teachers would name. The geography teachers got lost in the woods and fell into bear traps. People were usually quite pleased to see them. They taught children enough to shut them up, which was the main thing, after all. But they always had to be driven out of the villages by nightfall in case they stole chickens." ‎- Soup