The Mundane Shell is a vast Concave Earth, an immense
   Harden'd Shadow of all things upon our Vegetated Earth,
   Enlarg'd into Dimension and deform'd into indefinite Space,
   In Twenty-seven Heavens and all their Hells, with Chaos
   And Ancient Night and Purgatory. It is a cavernous Earth
   Of labyrinthine intricacy, twenty- seven folds of Opaqueness,
   And finishes where the lark mounts.
   
   William Blake