Collect 'em all!
Reginald Scot
(c.1538 – 9 Oct 1599)
Birthplace: England (specific location undocumented)
Profession-changing contribution: Scot was not a magician or illusionist. An educated man of the upper-class, he published a book The Discoverie of Witchcraft, in 1584, that challenged the belief in witchcraft.
A portion of the text details how some acts of conjuring performed in public were actually illusions using mechanical devices and other simple deceptions. It's now considered the first (unintentional) instruction manual for illusionists.
Scot's accusation that the Roman Catholic church was to blame for the punishment of "witches" and witch-hunt culture in general, did not go over well with authorities. When James I rose to power, copies of the book were burned.
Fun fact: Scot also wrote the first instructional volume about hops cultivation, Perfect Platform of a Hop-garden.
Bonus fun fact: The full title of Scot's witchcraft-debunking text is, The Discoverie of Witchcraft, wherein the Lewde dealing of Witches and Witchmongers is notablie detected, in sixteen books … whereunto is added a Treatise upon the Nature and Substance of Spirits and Devils.
Editor's note: We couldn't find a suitable image of the cover of Mr. Scot's book, and there are no portraits of Scot available. However, you can read excerpts from Discoverie of Witchcraft here and here.