Top Hat Illusion

Did you know that there is a famous illusion associated with Lincoln’s hat?

Consider the size of this president’s stove pipe hat. Namely it’s height, and it’s width including the brim. Is the hat taller than it is wide?

The hat is exactly as tall as it is wide! Use the little plan view below to help understand the rule of illusion as it applies here. Lines A—B and D—C are equal length. A horizontal line A—B will always appear shorter when interrupted by an identical, but perpendicular line D—C.