In 1680 he published his prayer-book under the title Kern aller Gebete in Jena. In 1689 he became vicar of St. Maria Magdalen, Breslau. His observations on the city's mortality rates resulted in the treatise “Reflexionen über Leben und Tod bey denen in Breslau Geborenen und Gestorbenen” which he finally sent to Leibniz – the covering letter is documented, the text itself is lost. Leibniz seems to have informed the Royal Society of Neumann's work. The society's secretary Henri Justel invited Neumann in 1691 to provide the Society with the data he had collected. Neumann's mail is lost, Edmond Halley's computations digesting Neumann's data have, however, survived – published in the Transactions of the Royal Society of 1693. In 1697 Neumann was appointed inspector of the Protestant schools and churches of Breslau. He eventually became vicar of St. Elisabeth and professor of theology at both the city's grammar schools. Neumann influenced Johann Christian Kundmann, who later published the first German comparative study of mortality rates in the Sammlung von Natur- Medizin- sowie auch dazu gehörigen Kunst- und Litteraturgeschichten ff. Neumann left a legacy of more than 30 hymns, many of which were included in Burg’s Gesang Buch and in the ninth edition of the Breslau Vollständige Kirchen-und Haus-Music He was also known for his theory that the individual Hebrew letters had "hieroglyphic" meanings. The letter aleph, for instance, representing the idea of activity, beth, the idea of three dimensions, etc. Around 1712, Isaac Newton wrote to Neumann, acknowledging receipt of his book, Clavis Domus Heber, and congratulating him on the endeavor, but professing himself insufficiently skilled in Hebrew to make a responsible judgment as to its success.
Genesis linguae sancte V T: Perspicue docens Vulgo sic dictas Radices non esse vera Hebraeorum Primativa; Sed Voces, ab alio quodam, Radicibus his priore & Simpliciore Principio deductas. Nuremberg, 1696 .
Bigam Difficultatum Physico-Sacrarum: De Gemmis Urim & Tummim... & De Cibo Samariae obsessae... Una cum Responsione ad Quaestionem amici, num Potus, Caffe dicti, aliqva in Sacris dentur vestigia? 1709.
Clavis Domus Heber. 1712.
Literature
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Schimmelpfennnig, K. A., "Kaspar Neumann ", in ADB, 23.
Lischke, Ralph-Jürgen, Caspar Neumann. Ein Beitrag zur Geschichte der Sterbetafeln, ed. Institut für Angewandte Demographie GmbH.