Countess Teleki was born Jane Frances Bickersteth in Britain in 1836 and married the Hungarian/Romanian Count Alexander Teleki in 1857. She corresponded with Babbage frequently concerning the Analytical Engine writing in 1862:
The more I think of it, the more I am distressed at your thinking it possible that you should give up the Analytical Engine. To strangle an idea and a great invention after so much pains to bring it to perfection, appears to me a kind of moral murder, and an inquiry to the whole human race, which it cannot be right to inflict... It is certain that you, and you only, are capable of completing the Analytical Engine, which if you abandon it, must perhaps remain unrealized for ages, and great though it be to conceive an idea hundreds of years in advance of one's kind, it surely is greater, by realizing that idea, to make the human race, in one generation, outstrip the progress of many.
Babbage replied: "I find no flaw in your reasoning about the Analytical Engine; I admire it; but you are aware that it rests entirely on the hypothesis that I care for the 'whole human race'".
Babbage was continually refining plans for the Analytical Engine (up to his death) and the Countess attempted to persuade him to actually build it writing in 1863:
I am very glad to hear your progress has been so satisfactory, and I hope that as you have now arrived at the ultima Thule of simplicity you will now really make the engine without searching further improvements. Don't forget the proverb I have often already quoted to you: le mieux est l'ennemi du bien.
The Countess' quotation from Voltaire would be translated into English as "The better is the enemy of the good."
All three of the women important in Babbage's life (if I exclude his mother who was very supportive of her son) preceded him to the grave. His wife, Georgiana died age 31, Ada Lovelace died aged 36 and Countess Teleki died a year before Babbage aged 34. It's sobering to think of the stunning rate of death associated with childbirth in the 1800s.
More about the Countess and Babbage can be found in Bruce Collier's excellent thesis on Babbage. He concludes his thesis writing:
In final conclusion, if one were to draw a moral from the history of Charles Babbage and his calculating machines, it would have to be that while there is certainly truth in Countess Teleki's maxim: "The Best is the enemy of Good", it is also true, as illustrated by Babbage's life and work, that "The Satisfactory is the enemy of the Marvellous".