Definition:Wallis's Number/Historical Note

Historical Note on using Newton's Method on $x^3 - 2 x - 5 = 0$
The cubic $x^3 - 2 x - 5 = 0$ was used by as a example to demonstrate how Newton's Method could be used to solve certain equations numerically.

It has subsequently been used as a test for a number of different methods of approximation.

Its real root is known to over $4000$ digits.