Two books on calculus by Leibniz were apparently published posthumously by his secretary Rafael Levi, see http://opac.tib.uni-hannover.de/DB=1/LNG=EN/CHARSET=iso-8859-1/CMD?ACT=SRCHA&IKT=1016&SRT=YOP&TRM=Raphael+Levi&Submit=go Does anyone know anything about those books? What's in them?

The main title of the two books seems to be:

Calculus differentialis oder Rechnung des Unendlichen des Herrn von Leibnitz

The books date from 1747 and 1776. Thus they appear to be different from the ones mentioned in Benakker's answer in the name of Schwarzschild. The title seems to suggest that the book originates with Leibniz and was edited by Levi. I haven't been able to get a pdf to see what the introduction says. If anyone has the pdf I would appreciate it.