Ancient Indians understood the concept of irrational numbers since Sulbasutra period. Rigveda gives rough value of Pi as 3 (Paridhiriva tritah). Bharatikrishnatirtha, the author of Vedic mathematics, quoted one shloka which gives the value of Pi correct up to 32 decimal places. Sulbasutras, Aryabhata and later astronomers knew the irrationality of Pi. Bhaskara I (628 AD) was the first to establish the concept that Pi is transcendental. Only in 1882 AD, F. Lindemann could prove that Pi is transcendental. Nilakantha(1444-1543 AD) was the first who explicitly defined the irrationality of Pi but modern textbooks give the credit to Johann Heinrich Lambert (1728-1777 AD), a Swiss mathematician for rediscovering the same in 1761 AD. In fact, Nilakantha must be given the credit being the first to discover it.