This was the plan: The president would take a friend’s yacht from New York to his summer home in Cape Cod. While at sea, a team of doctors would perform a major surgery through the roof of the president’s mouth. And there was an important directive: No matter what, the doctors could not touch the president’s trademark mustache.

President Trump raised eyebrows Saturday when he took an unscheduled trip to Walter Reed National Military Medical Center. He wasn’t seen in public afterward until Tuesday afternoon, fueling speculation that he may have a medical issue.

In a tweet, White House press secretary Stephanie Grisham dismissed that speculation as “irresponsible/dangerous rumors.” Trump was simply beginning “portions of his routine annual physical exam,” which wasn’t expected until the New Year, she said.

But if the president’s trip to Walter Reed wasn’t as Grisham claimed, well, it would follow a long tradition of presidents hiding medical conditions from the public, right down to disparaging members of the media asking questions.

One of the first to do this was President Grover Cleveland. The story of how this happened is the subject of the 2011 book “The President Is a Sick Man,” by Matthew Algeo.

Cleveland is the only president to have served two terms nonconsecutively. Shortly after his second inauguration in March 1893, he noticed a small rough spot on the roof of his mouth. By June, it was much larger.

A doctor diagnosed the tumor as cancer — a disease even more feared then than it is now.

At the time, the U.S. economy was declining and heading toward a depression. Cleveland feared — quite rightly, Algeo wrote — that if news of his diagnosis became public, the economic situation would get even worse.

Thus, the plot to treat Cleveland on the yacht.

The surgery was performed aboard the yacht Oneida on July 1, 1893. A team of six surgeons took only 90 minutes to extract the tumor, five teeth and large section of Cleveland’s left jawbone — all through the roof of his mouth.

“The doctors took incredible risks. I mean, it was really foolhardy,” Algeo told NPR in 2011. “I talked to a couple of oral surgeons [while] researching the book, and they still marvel at this operation: that they were able to do this on a moving boat; [that] they did it very quickly.”

A few weeks later, a rubber prosthetic was added to fill the space in his mouth. Cleveland made a remarkable recovery, and for a time it seemed the public was none the wiser.

Then, on Aug. 29, the Philadelphia Press published what Algeo calls “one of the greatest scoops in the history of American journalism.” The president, the newspaper reported, had had surgery to remove a cancerous tumor aboard his friend’s yacht. The reporter, E.J. Edwards, knew everything, right down to the names of each doctor on board.

The news spread to papers across the country, threatening to unleash the panic Cleveland had feared. “It is sincerely to be hoped that the operation will prove successful and the President will live many years,” the Londonderry Times said. The Indianapolis Journal worried that even after surgery the cancer might be “lurking in his blood” and “would develop into a dread and mysterious enemy.”

Cleveland’s associates kicked into high gear. The lead doctor, Cabinet officials and a presidential aide all released statements saying the story was untrue. A newspaper editor who was close friends with Cleveland said the problem had been nothing more than a toothache.

Plus, there was seemingly no physical evidence. The president’s face appeared unchanged and his voice was as vigorous as ever.

Within the week, the papers turned against Edwards, denouncing the story as a “cancer fake” and “a deliberate falsification.”

“The story about the terrible cancer in President Cleveland’s cheek appears to be about as reliable as the yarns about his bulldozing Congressman,” the Salt Lake Herald said.

In the near term, Edwards’s reputation was ruined, but he lived long enough to be vindicated. In 1917 — 24 years after the surgery and a decade after Cleveland’s death from a heart attack — one of the surgeons on board published a book with the full details of the daring operation.

Edwards’s “dispatch was substantially correct, even in most of the details,” the surgeon said.

Read more Retropolis: