President Donald Trump raised eyebrows when he told French firefighters to move "quickly" and possibly use aerial water tankers to save Notre Dame. But it was hardly the first time he has come forward as an unlikely expert.
Monday's tweeted advice got short shrift from French authorities racing to save the renowned Paris cathedral.
Bombardment with large quantities of water from airplanes could have flattened the 850-year-old building, French emergency services said.
Trump's confidence in his eclectic knowledge base, however, is unlikely to have been shaken.
Here are some other nuggets of wisdom from a president, lifelong real estate developer and former TV show host whom The Washington Post accuses of having made more than 9,000 false or misleading statements in two years.
Trump is worried about aerospace giant Boeing's reputation following two recent crashes of the 737 MAX model. He also has a solution: change the name.
"What do I know about branding, maybe nothing (but I did become President!), but if I were Boeing, I would FIX the Boeing 737 MAX, add some additional great features, & REBRAND the plane with a new name," Trump tweeted. "No product has suffered like this one. But again, what the hell do I know?"
Citing widely disproven or unproven theories, the president says wind turbine energy cannot handle variations in output -- and is bad for you.
"If it doesn't blow, you can forget about television for that night," he told a rally, imitating a couple relying on wind-generated power.
"Darling, I want to watch television.' 'I'm sorry! The wind isn't blowing.' I know a lot about wind."
"The noise causes cancer."
Although mostly known for his work with buildings and golf courses, Trump has quite a bit to say about aerospace.
Musing earlier on the Boeing 737 MAX tragedies, Trump tweeted: "Airplanes are becoming far too complex to fly. Pilots are no longer needed, but rather computer scientists from MIT. I see it all the time in many products. Always seeking to go one unnecessary step further, when often old and simpler is far better."
He's also shared his expertise on drones at a cabinet meeting:
"I know more about drones than anybody."
But Trump sees himself equally as standing up for rather older technology, like walls on the US-Mexican border.
"Nothing (else)... will work, and that has been true for thousands of years," he tweeted. "I know tech better than anyone."
If Trump has unusual smarts, he knows why.
"My uncle was a great professor and scientist and engineer, Dr. John Trump at MIT; good genes, very good genes, OK, very smart," he said in a speech.
"If I ran as a liberal Democrat, they would say I'm one of the smartest people anywhere in the world - it's true!"
But even if the president is an expert, he doesn't trust regular experts -- like the ones he says have been giving bad foreign policy advice to his predecessors in the White House.
"You know, I've always wanted to say this -- I've never said this before with all the talking we all do -- all of these experts... The experts are terrible," he said in a speech.
In fact, he suggests that it would be better if he were left in charge of thorny issues like the battle with Islamic State and other radical Islamist jihadist groups.
"I know more about ISIS than the generals do," he told a rally