Oh my God, one poem is indeed impossible, and it’s a good thing I’m far away from my bookshelves or I would be paralyzed, but off the top of my head: Rilke’s Duino Elegies, Jim Harrison’s The Theory and Practice of Rivers, Leonard Cohen’s Travel, most of Pablo Neruda. I spent a long love affair once communicating via a secret postcard code that employed Neruda’s 100 Love Sonnets. They will bring you to your knees: "I loved you without knowing I did … I broke into houses to steal your likeness …"