Not without reason is it said that no one who is not conscious of having a sound memory should set up to be a liar.
--"On Liars" from Michel Montaigne's Essays.
I crashed into this awful sentence last year while reading Montaigne's Essays. I've gone over it more than fifteen times and I still haven't a clue what it means.
I don't care if Montaigne is one of the 16th Century's greatest thinkers. What kind of douchebag uses two double negatives in the same sentence? How could anyone do this to their readers and keep a clear conscience?
Write like this at your peril. I don't care how smart you think you are, no one should have to waste their time and mental bandwidth deciphering your writing. Go over every single one of your sentences and make sure each says exactly what you mean it to say. And then do it again to catch the sentences that you missed the first time.
No reader should be abused by arrogant sentences like this.