Elon Musk is know for a lot of things, but an insane work ethic is near the top of the list.

"Nobody ever changed the world on 40 hours a week," he's said more than once. Of course, he also gave an interview in which he noted the toll this takes.

"No one should put this many hours into your work," Musk told Axios on HBO. "This is not good. People should not work this hard. ... It hurts my brain and my heart. ... There were times when I was working literally 120 hours. This is not recommended for anyone."

Good or bad, where did Musk get this insane work ethic to begin with? 

Well, if you ask his mom, she'll say she had something to do with it. 

(Bonus content: You're invited to download How to Raise Successful Kids (7th Edition), which is my free e-book full of related content on best practices and advice for raising kids.) 

Elon Musk's mom

Maye Musk, 73, is a Canadian-born model and dietician, and the mom to Elon Musk and his brother, Kimbal Musk, and their sister, Tosca Musk. 

Maye Musk has a new book out, and she wrote an essay for CNBC in advance of the launch about the keys to raising Elon Musk and his siblings.

Short version: "I did it by teaching them about hard work and letting them follow their interests."

'A terrible human being.'

Elon Musk's story is a bit complicated: He was born to Maye Musk and Errol Musk in South Africa, and when his parents divorced when Elon Musk was about 9, he went to live with his father.

Errol Musk was "a terrible human being," Elon Musk said in an interview with Rolling Stone

After high school, Musk moved to Canada (he had citizenship through his mom), and his mother and siblings followed him soon after.

'I never felt guilty'

Against that backdrop, Maye Musk writes in her essay that she always had to work as a single mother, and she "never felt guilty ... because I didn't have a choice."

It's a short essay, but breaking it down, it seems there are five key things Maye Musk says she did, to raise successful kids:

1. Put them to work at an early age.

Maye Musk cites a few examples here, but let's just say that whether she knew it or not, requiring her kids to work from an early age squares with the science. 

One study shows that kids who do chores wind up becoming more successful adults.

2. Treat them like adults.

Looking at Elon Musk's childhood, it does seem like he had to grow up in a hurry. Maye Musk seems to regard that as a feature, not a bug, of her parenting style.

"My parents treated us like adults who could be trusted," she writes, "and their influence is evident in how I raised my children.

3. Let them follow their interests.

"I never told them what to study. I didn't check their homework; that was their responsibility," Maye Musk wrote.

It seems to have worked, given the insane number of hours Elon Musk reportedly spends in his factories.

4. Don't get them used to luxuries.

Maye Musk seems to be a big proponent of not spoiling your kids or letting them get used to high end luxuries before they can afford them. As long as they're safe, she writes, "let them look after themselves."

She added: "When they went to college, they lived in quite poor conditions: mattress on the floor, six roommates or a dilapidated house. But they were fine with it. If your children aren't used to luxuries, they survive well."

5. Make them responsible for their own futures.

Her parting advice: Basically it's "don't worry."

So many parents get easily stressed about their kids," she writes. "My advice? Let your kids ... be responsible for their future. ... Teach your children good manners. But let them decide what they want."