Paul Amadeus Dienach
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Paul Amadeus Dienach was supposedly a time traveller.  His writings, in diary form, were translated by Georgios Papachatzis in 1940s and remained hidden until the 1970s when was finally published as Chronicles From The Future: The amazing story of Paul Amadeus Dienach. 
In 1921, Paul Amadeus Dienach, a Swiss-Austrian teacher fell into coma for a year. When he woke up, he began writing a diary that he kept secret until he contacted one of his students, Georgios Papachatzis, to translate it and keep it secret. In his writings, he claims to have awakened in the body of a man, Andrew Northman, in the year 3906 AD. According to the author, when awakened in the future, people realized that it was not Northman, and told him the events during the future period.