From Robert Heinlein’s “Stranger In A Strange Land” :
Jubal found Mike stripped down and the ship’s surgeon looking baffled. “Doctor,” Nelson said, almost angrily, “I saw this patient only ten days ago. Tell me where he got those muscles?”
“Why, he sent in a coupon from the back cover of Rut: The Magazine for He-Men. You know, the ad that tells how a ninety-pound weakling can-“
“Doctor, please!”
“Why don’t you ask him?” Jubal suggested.
Nelson did so.
“I thinked them,” Mike answered.
“That’s right,” Jubal agreed. “He ‘thinked’ ’em. When I got him, just over a week ago, he was a mess, slight, flabby, and pale. Looked as if he had been raised in a cave-which I gather he was, more or less. So I told him he had to grow strong. So he did.”
“Exercises?” Nelson said doubtfully.
“Nothing systematic. Swimming, when and as he wished.”
“A week of swimming won’t make a man look as if he had been sweating over barbells for years!” Nelson frowned. “I am aware that Mike has voluntary control over the so-called ‘involuntary’ muscles, But that is not entirely without precedent. This, on the other hand, requires one to assume that-“
“Doctor,” Jubal said gently, “why don’t you just admit that you don’t grok it and save the wear and tear?”
Stranger In A Strange Land – Robert Heinlein @ archive.org or more interestingly you could read it with real paper in hand – I linked the digital copy anyway.
Meditate (until you grok) on thinking yourself muscular.
The main character isn’t the only one in the book who does.
Since first having read the book as a teen, the quoted passage, and what possibility it implies has stuck with me.
I’ve internalized belief that I can think myself fit. This passage caused a big philosophical dawning in me of my true physical potential. Human potential as designed by God is ∞, greatness is within your grasp. Think only of high possibility! We are capable of far more than science currently knows.
Read the book.
-J