A newly reported investment round has brought in $112.5 million for the Boring Company, the venture that billionaire techie Elon Musk created last year to build transit tunnels.

And most of those millions came from Musk.

Documents filed today with the Securities and Exchange Commission say 31 unnamed investors contributed to the funding round.

Musk himself put in more than 90 percent of the money, according the Boring Company. The company said the rest came from early employees, with no involvement by venture capitalists or outside investors.

For what it’s worth, the filing lists two executive officers: Jared Birchall, who’s connected to another Musk-supported startup called Neuralink; and Steve Davis, who has served as director of advanced projects at SpaceX, one of Musk’s best-known companies (along with Tesla).

The Boring Company seemed like a lark when Musk unveiled it to the world last year. It built on his personal fascination with tunnels and rapid-transit schemes like the Hyperloop concept, and he said it took up only about 2 percent of his time.

A lot has happened since then:

Those sales campaigns appear to be the only revenue generators to date. All the digging projects are being done without significant public funding, which suggests that Musk has already paid out millions to support the company’s employees and equipment purchases.

Last month, Musk shifted the focus of his tunnel vision to prioritize transporting pedestrians and bicyclists rather than cars. “It’s a matter of courtesy and fairness,” he explained in a tweet. “If someone can’t afford a car, they should go first.”

It’s not clear how long it will be before any of the Boring Company’s tunnels are open to the public, on foot, on bikes or in cars. But the $112.5 million appears to take the Boring Company out of the humorous-hobby category and put it in the serious-business category.