There’s an old story about two men on a train. One of them, seeing some naked-looking sheep in a field, said, “Those sheep have just been sheared.’; The other looked a moment longer, and then said, “They seem to be — on this side.” It is in such a cautious spirit that we should say whatever we have to say about the workings of the mind.
John Holt, How Children Learn WP
And since we’re at it, I might as well show off my other train-and-grazing-animals-through-the-window joke:
Two Englishmen are going by train. A conversation isn’t getting on. The train passes a meadow, on which a herd of sheeps pastures. One of the passengers says:— 1356.
The other man is surprised, but gives no answer. In some time the train passes another pasture. The first passenger says:— 1693.
His neighbor brakes and asks:— Sir, our train moves at speed 60 miles per hour. How can you count so quickly? — Oh, sir, it’s very simple! First I count a quantity of legs in a herd and then I divide this number by four.
All Elementary Mathematics, New method of fast calculus