Some claim that mail art, an art form that uses the postal system as a medium, began when Cleopatra had herself delivered to Julius Caesar in a rolled-up carpet, but the thousands-strong, international network of mail artists as it exists today is a more recent development, evolving between the 1950s and 90s. Mail artists typically exchange ephemera in the form of decorated envelopes, illustrated letters, artist trading cards, and many other items. Who is deemed the pioneer of modern mail art? Discuss