Doris Lessing wrote:
In mental hospitals where the millions who have cracked, making cracks where the light could shine through at last, the pills are like food pellets dropped into battery chickens’ food hoppers, SLEEP, the needles slide into the outstretched arms, SLEEP, the rubber tubes strapped to arms drip, SLEEP.
in Briefing for a Descent into Hell, 1971. Twenty years later Leonard Cohen would rediscover a similar turn of phrase: “There is a crack, a crack in everything. That’s how the light gets in.”
Over at Genius, as per ushe a bastion of wrongness, the current annotation on Cohen’s song is:
“Blessed are the cracked, for they shall let in the light.” — Groucho Marx
This idea that cracks are essential for light getting in is not very new. Leonard Cohen may have gotten it from the book “A Path with Heart” by Jack Kornfield that mentions a monk with a broken leg who kept drawing cracked vases because “that’s how the light gets in”.
That’s probably a tail wagging a dog because Kornfield’s book came out a year after Cohen’s anthem.
Searching for the Groucho Marx quote, I find a ton of references to it but I’m not sure when and where he said it. He might’ve been the Quelle Q that inspired both Lessing and Cohen.