Wallis
(1) Born at Ashford, Kent, November 23, 1616; died at Oxford, October 28, 1703.
(2) According to the Dict. Nat. Biog. Older authorities give 1654.
(3)Arithemetica Infinitorum, sive Nova Methodus Inquirendi in Curvilineorum Quadraturam, aliaque difficiliora Matheseos Problemata, Oxford, 1655.
(4) The Latin edition is in volume II of his Opera Mathematica, Oxford, 1693-1695.
(5) D.E. Smith, in the Bulletin of the Amer. Math. Soc., XXIV (2), p. 82.
(6) See his Opera Mathematica, I, 441, where he explains that he uses a small square for a symbol for the ratio of the square on the diameter to the area of the circle. In our symbolism this is 4(r^2): pi(r^2 ), or 4: pi. On page 469 he gives the value stated above. See also his Volume II, cap. lxxiv.