Back when going "viral" had less exciting connotations - back when tweeting someone meant getting to the nearest telegraph - magicians and entertainers alike had to use other marketing techniques to lure people to their shows. A popular approach (and still is) was to hire artists to create sensational posters to advertise their upcoming shows. These posters were traditionally made using a long and arduous process called stone lithography. Magicians and mentalists like Houdini, Kellar, Alexander and Thurston all created stunning (and often exaggerated) images that have stood the test of time. Their vibrant colors, stunning composition, and simplistic tag lines piqued the public's curiosity. Memorable phrases like "The Man Who Knows", "Do The Spirits Return?", "Death Defying Mystery" or "Wonder Show of the Universe" all make our eyebrows raise.
Occasionally billboards and posters were made to depict a feature act that distinguished each performer from their competition. Harry Houdini often teased the dangerous escapes he performed nightly (as seen in the famous milk can poster above). Harry Kellar is thought to have popularized the depiction of the devilish imps in his designs. These imps were swiftly replicated and copied by almost all the other magicians in that era (and still repeated ad nauseam by some today).
My favorite design? This "Ask Alexander" billboard which is displayed in one of my favorite spots - Brooklyn Bowl. You'll have to see it in person to get the full hypnotic effect.