Enthusiasm for a wealth tax on the country’s thin sliver of multimillionaires and billionaires may be unsurprising — after all, most Americans wouldn’t have to pay it. But now the idea is attracting support from a handful of those who would.

A letter published Monday on the website Medium.com calls for “a moderate wealth tax on the fortunes of the richest one-tenth of the richest 1 percent of Americans — on us.”

The “us” includes self-made billionaires like the financier George Soros and Chris Hughes, a Facebook co-founder, as well as heirs to dynastic riches like the filmmaker Abigail Disney and Liesel Pritzker Simmons and Ian Simmons, co-founders of the Blue Haven Initiative, an impact investment organization.

“We thought it would be a good idea,” Mr. Simmons explained by phone as he waited out a traffic jam in the Boston area. “Liesel and I decided to reach out to some other folks to see if they thought it was a good idea, too.”