Charlie Munger and Warren Buffett are the two greatest sources of incredible investing anecdotes. From a small California-based chocolate company to an Illinois bank, and a small farm located somewhere in between, it seems that all these two touch turns to gold.

At a recent Daily Journal meeting of shareholders, Munger shared a small tidbit about one of the best investments he's ever made. It was 1962, and Munger was on the golf course with a new friend, Al Marshall.

Al Marshall had experience working for several oil producers, large and small. As oil was going through yet another bust at the time, Marshall was unemployed, but he was making investments on his own, buying up oil royalties at auction. Munger was then working as a real estate lawyer at a firm he founded -- he hadn't yet found Wall Street.

By hole No. 2, Munger was already asking Marshall about the oil royalties he intended to buy. By hole No. 3, Munger, confident to a fault and never one to mince words, told Marshall that he was structuring the deals all wrong. Marshall said that if Munger worked out the financing and the tax structure, he'd do the rest.

That's exactly what they did. As Munger described at the Daily Journal meeting this year, he and Marshall put up $1,000 each to buy oil royalties at auction. He described the auctions as a place for unsavory folks to do deals at prices that were much too cheap.

"I soon realized that under the peculiar rules of an idiot civilization, the only people who were going to bid for these oil royalties were oil royalty brokers who were a scroungy, dishonorable, cheap bunch of bastards. I realized that none of them would ever bid a fair price," he said at the meeting in February 2016.

His hunch was right. The royalties were very much underpriced, leading to some of the most incredible returns any investment could ever deliver.

He added that, for "many, many, years, the Mungers were getting $100,000 a year, 50 years later. More than 50 years later." The only problem he could find in the story is that "it only happened once," he told the crowd, laughing as he said it.

In the book Damn Right: Behind the Scenes with Berkshire Hathaway Billionaire Charlie Munger, published in 2000, Munger admitted that his family was still receiving $2,000-$3,000 checks each month from his investment in the trust, all from his original $1,000 investment. This is quite clearly one of the rare investments that knocks on your door. You won't find these advertised in a late night infomercial.

Munger pointed out that there is an important lesson to be learned in that life only gives you a few great opportunities in an average lifetime. "The trick in life is when you get the one, or two, or three that your fair allotment for a life is, that you've got to do something about it."

It seems unlikely that very many people will get the opportunity to put up $1,000 and collect 100 times more each year for a period spanning more than 50 years. That's certainly an outlier.

But it got me thinking about the small fortunes that far too many people pass up far too often, like a 50% match on a 401(k) plan at work, or an opportunity to parlay a small investment into a certificate to learn a new skill. Life is full of small decisions where the result is a big reward -- but only if we're willing to keep our eyes and ears open to them.