Author and Jewish convert to Christianity; born at Altorf at the end of the seventeenth century; died at Prague about 1740; probably a member of the Keyser family of Schleusingen (Bavaria). He claimed to have been a rabbi at Schleusingen before his baptism in 1715.
Christiani wrote: (1) "Kurze Beschreibung einer Jüdischen Synagoge und eine Beschreibung der Synagogalen Gebräuche" (Regensburg, 1723); (2) "Die Schlacht- und Visitir-Kunst" (ib. 1724); (3) "Ausgang von dem Verstockten Judenthum und Eingang zum Wahren Christenthum," an account of his conversion, his profession of faith, and several orations (Erfurt, 1720); (4) "Rede zur Einladung für Rabbinische Studien," written in Hebrew and German, inserted in Johann David Köhler's "Program" (Altorf, 1715); (5) a German translation of the"Sefer ha-Minhagim" of Jacob Levi (MaHaRIL), published at Bremen in 1733.