The Henneberg surface was the first known non-orientable minimal surface, first discovered by 1875, by Lebrecht Henneberg.
Until the 1981 it was the only known non-orientable minimal surface.
The Henneberg surface is topologically equivalent to the
Cross-Cap Surface, thus is a representation of projective plane.
The Henneberg surface was often studied due to its branch points (i.e. derivative
of the parametrization is zero). Branch points make visualizations of the surface
x = 2 * sinh(u) * cos(v) - 2 * sinh(3 * u) * cos(3 * v) / 3
y = 2 * sinh(u) * sin(v) - 2 * sinh(3 * u) * sin(3 * v) / 3
z = 2 * cosh(2 * u) * cos(2 * v)