Poe also incorporated the theories of Reynolds and John Cleves Symmes Jr. on the Hollow Earth. The theory of these works was that a hole at the South Pole led to the interior of the planet, where undiscovered civilizations prospered. As Symmes wrote, the earth was "hollow, habitable, and widely open about the poles". This theory, which he presented as early as 1818, was taken seriously throughout the nineteenth century. Symmes' theory had already served Poe when he wrote, in 1831, "MS. Found in a Bottle", based partly on "Symmes' Theory of the Concentric Spheres", published in 1826. "MS. Found in a Bottle" is similar to Poe's novel in setting, characterization, and some elements of plot. Other writers who later fictionalized this theory include Edgar Rice Burroughs and L. Frank Baum.