Seth Klarman, the value investing giant who draws comparisons to Warren Buffett, had some advice for the new president in his latest investor letter: Stop tweeting.
"Strikingly, the tweeting has continued, including patently false claims and personal attacks that have no place in a serious administration," writes the head of Baupost Group in the letter, a copy of which was obtained by CNBC.
Citing the work of behavioral psychologist Daniel Kahneman, Klarman notes that our first thought is "often not the best answer we ultimately arrive at."
So "this raises the question of whether it makes sense to tweet ... anything. Especially for a president," he says. "In a job where words matter and nuance matters more, tweeting is not a communication tool, it's pure indulgence."
The Boston-based hedge fund manager devotes a large portion of the 19-page letter to criticism and evaluation of Trump and the possible implications of the president's policy proposals. Klarman's annual letters are considered "must reads" by his large following on Wall Street.
"Why write so much about the recent presidential election in an investor letter? Because elections matter, and Trump is anything but business as usual. Much is about to be reshaped for business and the economy, potentially creating investment opportunities but also increasing uncertainty and elevating risks," the letter states.
CNBC's Jim Cramer and billionaire Mark Cuban gave Trump similar advice regarding Twitter recently, telling him he his only hurting his chances of implementing bold new economic policies by instead starting distracting controversies on the social media site.
As many call on Trump to stop tweeting, an analyst upgraded Twitter's stock Wednesday because the president uses the service so much, drawing increased interest in the company.
Baupost did not immediately return a call and email for comment.
— With reporting by CNBC's Michael Bloom and Tae Kim.