“It’s a device for making pictures quickly,” said Twoflower. “Quite a new invention. I’m rather proud of it but, look, I don’t think these gentlemen would—well, I mean they might be—sort of apprehensive? Could you explain it to them? I’ll reimburse them for their time, of course.” “He’s got a box with a demon in it that draws pictures,” said Rincewind shortly. “Do what the madman says and he will give you gold.”
