In the mid-19th Century, not long after the invention of photography, John Benjamin Dancer (1812 – 1887) began printing tiny photographs onto glass slides at his studio in Liverpool, England. In Paris, René Dagron (1817 – 1900) wondered how to circumvent the need for an expensive microscope to view them. In 1859, Dagron patented the first Stanhope lens mounted with a mini-photograph.
He named it after the magnifying device invented 50 years earlier by Charles Stanhope, Third Earl Stanhope (1753-1816). In the late-18th century, Stanhope invented lenses which allowed all sorts of “viewers” to house images in secret. Stanhopes, also called Bijoux Photomicroscopiques, became known as ‘peep holes’, ‘peep-eye views’ or ‘peeps’.
And this little piggy had a secret…
[Images & caption found here. More at the link.]