That quotation is in fact from "Wind, Sand, and Stars", the memoir of the same author.
On the same theme:
> the supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a single datum of experience
- Einstein
> I would have written a shorter letter, but did not have the time
- Pascal
> Simplicity is a great virtue but requires hard work to achieve and education to appreciate, and, to make matters worse, complexity sells better.
- Dijkstra.
Thank you! The GP quote sounded completely unLittlePrince-like! I can believe it as a quote from Saint-Exupery.