An apple a day ...

Looking for the origin of subject phrase.

From Random House Dictionary of Popular Proverbs and Sayings by Gregory Y. Titelman : "An apple a day keeps the doctor away. Eating fruit regularly keeps one healthy. First found as a Welsh folk proverb " 'Eat an apple on going to bed,/ And you'll keep the doctor from earning his bread.' First attested in the United States in 1913..."