You may well be right, in which case I don't agree with the present framing of WP:OR as it's being applied to mathematics articles. I don't consider it any more "original research" to invent an example like #7 than it is to invent a graphic showing the basic structure of a virus. In any case, I've seen the example of the cooks and their measuring jugs elsewhere, and it not infrequently appears in one form or another in IQ-type tests, so it's not an invented example anyway. But my fundamental position is that anyone who has followed the exposition of the algorithm to that point would have no difficulty in perceiving the truth of the statement, so a citation would only be there to reassure those who haven't understood what's been said. That's surely not the purpose of providing citations.  Fatuorum