Cellular Cosmogony, which is Teed's unique form of Hollow Earth theory which puts forth the idea that the Earth, and universe are contained within a concave sphere, or 'cell'. The Koreshans even conducted several experiments, similar to those conducted by believers in a Flat Earth. The most well known was conducted on the beach of Naples, Florida (the Koreshan Geodetic Survey of 1897), a town south of the Koreshan Unity commune at Estero, Florida. Here is the description of the earth from Cellular Cosmogony:

"The sun is an invisible
electromagnetic battery revolving in
the universe's center on a 24-year
cycle. Our visible sun is only a
reflection, as is the moon, with the
stars reflecting off seven mercurial
discs that float in the sphere's
center. Inside the earth there are
three separate atmospheres: the first
composed of oxygen and nitrogen and
closest to the earth; the second, a
hydrogen atmosphere above it; the
third, an aboron (sic) atmosphere at
the center. The earth's shell is one
hundred miles thick and has seventeen
layers. The outer seven are metallic
with a gold rind on the outermost
layer, the middle five are mineral and
the five inward are geologic strata.
Inside the shell there is life,
outside a void."

(from Wikipedia)