ABSTRACT
The original source of the 1670 yield approximation formula given in Hawawini and Vora [2] on page 149 and referred to on page 148 is a letter written by Isaac Newton to John Collins (Turnbull [3, pp. 24–25]). Hawawini and Vora incorrectly attribute the formula to John Newton. Also, the analytical solution to the implicit yield problem (Hawawini and Vora [2, p. 147]) can be traced to a letter written by Michael Dary to Isaac Newton, not John Newton (Turnbull [3, p. 326]). These errors were probably a consequence of the fact that de Morgan [1], who Hawawini and Vora use as a basic reference for the early history of yield approximations, did not clearly distinguish between the work of the two Newtons. John Newton was a minor scientist of the period.
