Jan Marek Marci (13 June 1595 – 10 April 1667), or Johannes (Greek: Ioannes) Marcus Marci, was a Bohemian doctor and scientist, rector of the University of Prague [1], and official physician to the Holy Roman Emperors (Ferdinand III [2] and Leopold I [3]). The crater Marci on the far side of the Moon is named after him, and he was the subject of a Czech Republic stamp in 1995.

Marci at some time came into possession of the Voynich Manuscript, apparently upon the death of its former owner, the alchemist Georg Baresch. He sent the book to his longtime friend Athanasius Kircher, with a cover letter dated 19 August 1666, or possibly 1665.

More details can be found on the Wikipedia page [4] (which has a list of his books), the Voynich Manuscript Biographies page [5], here [6] and on the Galileo Project [7].

A link to an image of the letter, now at the Beinecke Rare Book and Manuscript Library, can be found here [8]. Project Gutenberg has a text [9].