Any man who can drive safely while kissing a pretty girl is simply not giving the kiss the attention it deserves.

Found anonymously in newspaper columns from the early 1920s. Originally presented in dialogue format: "Dorcas—"Do you ever allow a man to kiss you when you're out motoring with him? Philippa—"Never, if a man can drive safely while kissing me he's not giving the kiss the attention it deserves."

It does not seem to have been attributed to Einstein until the 1990s (e.g. here).