Marci was born in Lanškroun, near the border between historical lands Bohemia and Moravia (presently parts of the Czech Republic).

He was also the personal doctor of Emperors Ferdinand III and Leopold I, and distinguished himself in the defense of Prague against the Swedish armies in 1648.

In October 1654 he was given the nobility title (falckrabě) "de Kronland" (anagram of "Landskron", German name for the city of Lanškroun).

[5][6] Marci's studies covered the mechanics of colliding bodies, epilepsy, and the refraction of light, as well as other topics.

[8] Marci at some time came into possession of the Voynich Manuscript, apparently upon the death of its former owner, the alchemist Georg Baresch.