Swing the image back and forth to create the illusion of moving wheels.  From the Duluth Herald, 1905.

From Physics, An Experimental Science by White, White & Gould, 1968.

The Mysterious Diamond Dye Imp, via Double-M.

From The Children's Newspaper, 1928.

At first glance, we assumed this was a Biblically-accurate angel.  It's an optical illusion of seven cherbus within a trinity, in a soap ad from Youth's Companion, 1887.

From Flying Saucer News, 1958.

"An optical illusion!!  Close your eyes and the white rectangle will turn black."  From Ya-Hoo, 1954.

They thought they could fool us, but we're not so easily tricked.  This is one of those optical illusions in which both figures are exactly the same height.  From National-Louis' 1964 yearbook.

You've seen the optical illusion asking whether it's two faces or a vase.  Actually, it's a bottle, and it's a drinking problem.

Optical illusions like you've never seen them, plus confirmation bias and the uncanny: it's Prof. Oddfellow's Penetralia.

An optical illusion -- can it be true that atheists will see only a series of lines?  From N. C. Wesleyan's 1977 yearbook.

I always flunk quizzes like this -- I invariably think it's two faces, but it's nearly always a vase.  Something about "negative capability" ... or was that another class? 

From the University of South Carolina at Spartanburg's 1973 yearbook.

From Lustige Blätter, 1903.

The peace angel is dead but appears to rise via a Pepper's Ghost illusion.  From Lustige Blätter, 1899.

From The Magician's Own Book, 1871.

"Weird phantoms of the air."  From Popular Mechanics, 1927.

The world / a skull.  An optical illusion from The Judge, 1917.