"Nova Methodus pro Maximis et Minimis" is the first published work on the subject of calculus. It was published in by Gottfried Leibniz in the Acta Eruditorum in 1684. It is considered to be the birth of infinitesimal calculus.
The full title of the published work is "Nova methodus pro maximis et minimis, itemque tangentibus, quae nec fractas nec irrationales quantitates moratur, et singulare pro illis calculi genus." In English, the full title can be translated as "New method for maxima and minima, and for tangents, that is not hindered by fractional or irrational quantities, and a singular kind of calculus for the above mentioned." It is from this title that this branch of mathematics takes the name calculus.
Although calculus was independently co-invented by Isaac Newton, most of the notation in modern calculus is from Leibniz. Leibniz's careful attention to his notation makes some believe that "his contribution to calculus was much more influential than Newton's."