Heinlein quote source

Ok, a friend of mine is looking for a Heinlein quote for a story.

It’s the one about ‘boys should be raised in barrels. When the turn 18 you can decide to let them out of stop you the barrel’. Something like that.

I’m on the road so I can’t look it up. Can sobeone toss me the full quote and the citation?

from The Rolling Stones:

“Pollux had his mouth open when his father again yelled, “QUIET!” He went on, “Edith, bring the barrel. This time we use it.” Mr. Stone had a theory, often expressed, that boys should be raised in a barrel and fed through the bunghole. The barrel had no physical existence.”

cf.

Mark Twain once said: “When a boy turns 13, put him in a barrel and feed him through a knot hole. When he turns 16, plug up the hole.”

You got that quick. I just reread “The Rolling Stones” a few months ago.

Google-fu!