Thoroughly interested, Eric took up a pile of colored strings, from the corner and started to convert his week's accounting into quipu. He worked for half an hour, but couldn't make it come out right. It proved an exasperating puzzle, because it seemed impossible and yet conveyed the suggestion that there ought to be some way of doing it. Already Eric had so keen a sense of the old man's comments that he hated to say that he couldn't do it. But, after a while, red in the face and quite ashamed, he said,
"I can't do it, Dan."
"No, he is not possible," said the puzzle-maker cheerfully. "That's what I wanted you to find. The quipu is wonderful but he's not wonderful enough, eh?"
"We'd have trouble trying to handle a big modern banking business by it, all right," the boy agreed. "But, Dan, how about this studying I'm supposed to do?"
"You know Latin numerals?" the old man replied.
"Of course!" Eric answered indignantly. "I couldn't even tell the time if I didn't!"
"Write 'Four,'" came the order.
Promptly the boy wrote "IV."
"Now look at watch."
"It's got four ones there," Eric said ruefully.