ln(2)=1 - 1/2 + 1/3 - 1/4   etc., etc.
copyright 1999

Pin Hole Camera
Note triangles ABC and DEF are similar and that the lengths A and E stay the same.
So B will be a harmonic sequence: 1, 1/2, 1/3, etc.
The picture of ln(2) is a perspective drawing of evenly spaced parrallel lines.