Franz Kessler
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Franz Kessler (ca. 1580-1650) was a scholar, inventor and alchemist living in the Holy Roman Empire.
He wrote a book called Unterschiedliche bisshero mehrern Theils Secreta oder Verborgene, Geheime Kunste (Various until now mostly hidden, secret arts), which was published in Oppenheim in September 1616. This book deals with creating communication codes.
In the same year he built an improved diving bell.