Think ghosts are real? According to one Victorian book, the spooky specters you encounter are just an optical illusion. 

Spectropia (full title: Spectropia, or, surprising spectral illusions showing ghosts everywhere and of any colour) was written by J. H. Brown and published in 1864. A firm disbeliever in the paranormal, Brown’s goal was to dispel the “absurd follies of spiritualism” by showing readers “the many ways in which our senses may be deceived.” Every single “ghost” sighting can be ascribed to properties of light, color, and the structure of the eyes—and Brown wanted to prove his explanation by providing readers with the chance to conjure their own colorful phantoms.

By staring at each ghost picture from Spectropia for about a quarter of a minute without blinking, dimming the lights, and then looking away from the book and toward a white wall, you’ll apparently be able to see the images of the ghosts “floating” in front of you. This phenomenon is thanks to an optical illusion called an “afterimage,” in which the eye adapts to overstimulation, loses sensitivity, and keeps seeing an image even when it’s no longer looking at it. Try it for yourself below. 

1. PLATE I

"This winged figure of Victory will give a white spectre by artificial light (rather green by daylight), the red wreaths green, the green roses red, and the orange stars blue."

2. PLATE II

"This black figure will give a white spectre."

3. PLATE III

"This will give a dark spectre."

4. PLATE IV

"This green figure will give a red spectre."

5. PLATE V

"And this red figure will give a green spectre."

6. PLATE VI

"This orange figure will give a blue spectre."

7. PLATE VII

"And this blue figure an orange spectre."

8. PLATE VIII

"This purple hand will give a yellow spectre."

9. PLATE IX

"And this yellow figure of Victory will give a purple spectre."

10. PLATE X

"The face of this figure will come out green in the spectre, the garment red, and the cloud white."

11. PLATE XI

"This black skeleton will make a white spectre."

12. PLATE XII

"This skeleton will also give a white spectre, with a yellow mantle."

13. PLATE XIII

"This figure and broom will give a yellow spectre, cloak and hat red, and moon white."

14. PLATE XIV

"These figures will give green and yellow spectres."

15. PLATE XV

"This Cupid will give a rose-coloured spectre, with bow and arrow yellow."

16. PLATE XVI

"This is a rainbow with colours reversed, the spectre of which will be found a good resemblance of nature, especially when seen on a cloudy sky."