The author of the letter, Gottfried Alois Kinner von Löwenthurn, was mathematical tutor to Archduke Karl Joseph von Habsburg (1649–1664), son of Emperor Ferdinand III. It was Kinner who suggested to Kircher that he construct the "Organum Mathematicum" as a learning tool for the young Archduke.
Kinner von Löwenthurn was born about 1610 in Reichenbach, Silesia, and was a Doctor of Theology, Philosophy and Law. He was in Prague around 1653.