quote from there, but the page explains it better "The KISS principle states that most systems work best if they are kept simple rather than made complicated; therefore, simplicity should be a key goal in design, and unnecessary complexity should be avoided." ^
"Leonardo da Vinci's "Simplicity is the ultimate sophistication", Shakespeare's "Brevity is the soul of wit", Mies Van Der Rohe's "Less is more", Bjarne Stroustrup's "Make Simple Tasks Simple!", or Antoine de Saint Exupéry's "It seems that perfection is reached not when there is nothing left to add, but when there is nothing left to take away". Colin Chapman, the founder of Lotus Cars, urged his designers to "Simplify, then add lightness". Heath Robinson machines and Rube Goldberg's machines, intentionally overly-complex solutions to simple tasks or problems, are humorous examples of "non-KISS" solutions.
A variant – "Make everything as simple as possible, but not simpler" – is attributed to Albert Einstein, although this may be an editor's paraphrase of a lecture he gave"