Vintage optical illusion skull postcards

Take a look at these fantastic vintage optical illusion skull postcards. These macabre beauties are from the early 1900s and all depict skulls with people woven into the imagery.

The people in the images are often placed so that their heads are in alignment where the skull's eyes would be. The last one is my favorite, where two girls sit beside their puppy, whose little face makes the skull's nose. Which one is your favorite?

From Instagram:

"Optical illusion skull postcards were incredibly popular in the early 1900s in Europe. They were Vanitas or Memento Mori – "Intended to cause the viewer to reflect on the inevitability of mortality and the consequent foolishness of all human ambition."