This is sort of an inside joke, but the formula which many people I know attribute to one C. Hamelly (if John Derbyshire's memory serves) was actually devised by Aristotle.
Just on an arithmetic note: The classical formula (due to Aristotle IMS) for ages of man and wife is X vs. (X/2)+7. So the ideal partner for a 35-yr-old woman would be a 56-yr-old man.
Its not ideal, just a reasonable limit. Or so I thought
Hi Monika!
Yeah, that's true. Hamelly's formula was that anything in this range is acceptable.