A medieval South Indian school discovered infinite series for π, sine and cosine — core ideas of calculus — long before Europe.
Mādhava of Saṅgamagrāma derived the infinite series now called the Leibniz series for π and the power series for sine and cosine; the Kerala school developed these systematically.
— Mādhava & the Kerala school (14th–16th c. CE); Yuktibhāṣā
Infinite series and the foundations of calculus (Newton & Leibniz, late 17th c.).
A genuine, defensible parallel.
Between the 14th and 16th centuries, the Kerala school of astronomy and mathematics — beginning with Mādhava of Saṅgamagrāma — derived infinite series expansions for π, sine, cosine and the arctangent, along with ideas about limits and term-by-term approximation that are recognisably the foundations of calculus. The 'Leibniz series' for π was Mādhava's centuries earlier.
This is well-established history. The careful caveat: the Kerala mathematicians developed powerful *series and analytical techniques*, but did not build the full general framework of the derivative and integral with the fundamental theorem of calculus that Newton and Leibniz unified. Whether their work transmitted to Europe is debated and unproven. Even so, this is one of the most underappreciated achievements in the history of mathematics — genuine pre-Newtonian analysis, done in India.