Very carefully, of course.

William-Adolphe Bouguereau’s “La Jeunesse de Bacchus” (The Youth of Bacchus), a joyful scene of mythological frolic, measures a whopping 20 feet long and nearly 11 feet high, and it was the biggest canvas he ever painted.

The 1884 work, with an estimate of $25 million to $35 million, will be a marquee offering at Sotheby’s Impressionist and Modern Art Evening Sale on May 14 in New York. (It will be on display from Friday through May 14.)

May events like the art fair Frieze New York and two prominent biennials — in Venice and at the Whitney Museum of American Art — keep the focus on contemporary art, but “La Jeunesse de Bacchus” is evidence of strong offerings of older works.

It will also rank as one of the largest pre-modern works offered in the history of Sotheby’s, sure to garner attention just for that fact, but also because it’s by a beloved 19th-century French painter who has a sterling sales record and legions of fans among museumgoers. (There’s a major exhibition of his work at the Milwaukee Art Museum on view until May 12.)

But to be viewed by prospective bidders and put on the block, it first had to travel from Paris.

Consigned by the painter’s heirs, the work hung in the same place for 135 years — Bouguereau’s studio in Paris’ 6th Arrondissement — and has been moved only three times previously, for exhibitions.

Overall, the job required around 20 people between the two locations, including a crane operator to get it out of the third-floor studio window and into a truck.

One of the conservators involved in the New York unpacking and restretching, Haley Parkes, called the whole process a “Bouguer-rodeo.”

Paintings of this size don’t wrangle easily.

Parkes’ father and business partner, Simon Parkes, a longtime expert in the field, said that it was the second biggest painting he had ever worked on, after a canvas by Jean-Michel Basquiat, and that the custom roller used to hold it in transit was the largest he had ever seen.

With “La Jeunesse de Bacchus,” Sotheby’s had a few built-in advantages.

Unusually for a painting of its age, “It has the original stretcher and hardware,” said Benjamin Doller, Sotheby’s chairman of the Americas and a longtime expert at the auction house specializing in 19th-century art. (To keep them taut, paintings are usually stretched onto a wooden armature in back.)

That meant that the wear and tear on it had likely been minimal, especially given that it had rarely been moved.

Doller had every reason to want the painting in good condition. He had big plans for the work, which is why he placed it in the Impressionist and Modern sale, despite its technically fitting into neither of those categories.

“We need to make sure the world’s wealthiest buyers have access to it,” Doller said of the sale placement. “It’s another level of validation.”

Bouguereau was the most important of the so-called academic painters of France in his day, those who adhered to traditional styles and techniques.

The artist painted around 750 works, said Louise d’Argencourt, an independent curator and expert in his work.

“Not a lot of them exist in private collections,” d’Argencourt said, adding that they have largely made their way to museums.

Bouguereau was the opposite of a starving artist. He was from a well-off family, and he made it even richer with his success.

“Americans were his biggest market, and for Knoedler Gallery, he was the No. 1 seller,” Doller said, referring to the now-defunct New York dealer that was once a dominant force.

“La Jeunesse de Bacchus” took Bouguereau almost three years to paint, and he did it without the benefit of assistants. He priced the work at 100,000 francs — an astronomical sum at the time that would have made it one of the most expensive paintings ever sold, Doller said — and he received an offer of 70,000 francs but rejected it.

“He said, ‘I get so much enjoyment, I’ll just keep it,’” Doller said. His descendants were wealthy enough to leave it where it was, but eventually the current generation decided to sell.

That led to the beginning of the Bouguer-rodeo in January.

It took 2 1/2 days for a Paris-based conservator and shipping crew to pack it up, starting with building scaffolding just to get the painting off the wall. The process was almost delayed by snow, which stopped just in time for the crane operator to lift the components outside.

Three crates were necessitated — one each for the frame, stretcher and canvas — and together they weighed almost 2 tons.

When they arrived in New York, the crate holding the canvas was opened by Sotheby’s art handlers, and a group peered inside. Concerned looks turned to smiles. The painting roller had a thin white plastic covering to protect it, and it was tied with five perfect bows.

“Only the French would do bows like that,” Doller said.

The elder Parkes proclaimed it “the Louis Vuitton of packing jobs.”

He added of the thick, ornately carved and gilded frame, which was packed in several pieces: “It’s in great condition. To make this frame today would cost half a million dollars.”

Then his son said, “Can we get the muscle men?” referring to the art handlers, and the roll was taken out and unfurled slowly so the image was facedown on the floor, with the white plastic providing a protective layer between the painting and the carpet.

The process was delicate enough that Sotheby’s chief executive, Tad Smith, stopped in to watch for a while.

The painting was deemed admirably even — no bumps or distorted areas — and was left to lie flat for a while.

The back of the canvas would tell the tale. “Dust can accumulate under the stretcher bar, and it can hold moisture,” Simon Parkes said. “Water is the biggest problem.”

Of great concern were the “tacking edges” — the extra part of the canvas beyond the image that folds around the back and is tacked to the stretcher.

“It carries all the weight,” Simon Parkes said, but added that the artist seemed to have put on his paint rather thinly.

He added that his job required a certain worrywart quality.

“Sometimes paint cracks or becomes unstable; those are common problems,” he said. “I’m only really interested in the stuff that can go wrong. We have to stay a step ahead.”

Then they were joined by Jamie Martin, the head of Sotheby’s scientific research department, who was carrying an ultraviolet light.

Martin noted that the lining had been reinforced and patched, and he took a tiny sample.

“We have to know what will stick to what,” Martin said of the painting’s eventual restretching. “The question is, is it wax resin or glue paste? And I don’t guess — I analyze it with straight-up science.” (It turned out there were two waxes and one synthetic adhesive.)

A few days later, the painting was placed back on its stretcher, and it went on view in March for the first time.

Now the only issue is finding a buyer with ambitions big enough to match the painterly craft behind “La Jeunesse de Bacchus” — not to mention the effort it took just to get it on the block.

This article originally appeared in The New York Times.