This article confirms that the common lore is broadly correct. Newton bought, stock goes up, Newton sells, realizes huge gains, stock goes up more, Newton buys again, stock crashes, Newton loses big.
This particular stock was a massive bubble though.
He only missed mutual funds (or a reasonable analogue thereof) by 50 years or so, though presumably he'd have had trouble investing in _Dutch_ ones.
(I'm not sure if he actually derived earth's, but he was aware of escape velocity as a concept.)