"Leaves of Grass," first published in 1855, contained twelve long untitled poems, but Whitman continued to expand it throughout his life. Whitman's poetry was unprecedented in its unapologetic joy in the physical and its inextricable link to the spiritual. As Ralph Waldo Emerson wrote to him: "I am very happy in reading ["Leaves of Grass"], as great power makes us happy ... I find incomparable things said incomparably well, as they must be."