  The Mercator projection is sometimes confused with another mapping technique,
specifically the central cylindrical projection, which projects the Earth's
surface onto a cylinder tangent to the equator, as if a light source is at the
Earth's center. Accidentally, this misconception is rather close to a truth.
The only operation that the map needs is a free bending in a uniform
gravitational field if the map's material is dense and soft enough to produce a
catenary profile. The north and south edges of the map should be parallel and
placed in the same plane at the appropriate distance. In this case, the bent
map been projected onto this plane gives the Mercator projection. This property
is rather curious, since it allows to make such a sophisticated one-to-one
mapping as the Mercator projection using simple tools available in the
workroom.
