La perfection est atteinte non quand il ne reste rien à ajouter, mais quand il ne reste rien à enlever...
This translates as
Perfection is attained not when there is no longer anything to add, but when there is no longer anything to take away...
See also: LessIsMore, ShakerQuote, TimeToMakeItShort
The full page on which this quote originates will be of interest to readers of this site and is quoted here in the interests of fair use.
In anything at all, perfection is finally attained not when there is no longer anything to add, but when there is no longer anything to take away, when a body has been stripped down to its nakedness.
It results from this that perfection of invention touches hands with absence of invention, as if that line which the human eye will follow with effortless delight were a line that had not been invented but simply discovered, had in the beginning been hidden by nature and in the end been found by the engineer. There is an ancient myth about the image asleep in the block of marble until it is carefully disengaged by the sculptor. The sculptor must himself feel that he is not so much inventing or shaping the curve of breast or shoulder as delivering the image from its prison.
In this spirit do engineers, physicists concerned with thermodynamics, and the swarm of preoccupied draughtsmen tackle their work. In appearance, but only in appearance, they seem to be polishing surfaces and refining away angles, easing this joint or stabilizing this wing, rendering these parts invisible, so that in the end there is no longer a wing hooked to a framework but a form flawless in its perfection, completely disengaged from its matrix, a sort of spontaneous whole, its parts mysteriously fused together and resembling in their unity a poem.
Meanwhile, startling as it is that all visible evidence of invention should have been refined out of this instrument and that there should be delivered to us an object as natural as a pebble polished by the waves, it is equally wonderful that he who uses this instrument should be able to forget that it is a machine.
See also: WikiMaster, CookDingThere is not a single English translation for this French quote. I've seen it as "Perfection is attained", "Perfection has been attained", etc. Perhaps DeSaintExuperyOnPerfection? would be a better PageName?
You're right, "attained" is better. I originally named this page PerfectionIsAchieved so references to it could easily be used in conversation, but feel free to re-name it.