This Poem is referred to by Eternal Sunshine of the Spotless Mind
This poem is where the title of the movie comes from, and is mentioned as Mary reads to Howard a quote taken from Alexander Pope's poem Eloisa to Abelard. "How happy is the blameless vestal's lot! / The world forgetting, by the world forgot / Eternal sunshine of the spotless mind! / Each pray'r accepted, and each wish resign'd."
Eloisa to Abelard is an Ovidian heroic epistle inspired by the 12th-century story of Héloïse's illicit love for, and secret marriage to, her teacher Pierre Abélard, perhaps the most popular teacher and philosopher in Paris, and the brutal vengeance her family exacts when they castrate him, even though the lovers had married.