High on a green sweep of Swiss Alps, grazing with a herd of goats, Thomas Thwaites is on all fours — dressed as one of them.

“Sweat is dripping off the end of my nose,” Thwaites writes in his new book, “Goat Man: How I Took a Holiday From Being Human” (Princeton Architectural Press). “My arms are on fire, and I can’t really feel my knuckles, but I imagine there’s not all that much skin left on them.”

After months of preparation, Thwaites had finally achieved his goal: to become a goat. Researching their thought patterns, he learned that goats are most likely “stuck in time, not able to think about the future or the past much, because they probably don’t have episodic memory.”

But why did Thwaites want to become a goat?

In 2014, the 33-year-old British freelance graphic designer was in debt, living with his father, and sending out résumés to no avail. With so much worry on his mind, he thought it would be wonderful to “step away from the complexities of the world and have a lovely holiday, not just . . . away from your job (if you have one), but away from your very self.”

Originally, he sought a grant allowing him to become an elephant and cross the Alps. “I’d . . . adapt my bipedal anatomy to that of a quadruped . . . develop an artificial prosthetic stomach that would enable me to eat and digest grass . . . adapt my sight and hearing and retrain my senses . . . so as to experience life from the perspective of an elephant.”

But he soon saw flaws in his elephant plan. Visiting South Africa and viewing the animals up close, he realized he would need to build the equivalent of a small car to become one, and also learned that elephants felt pain and sadness much like humans. A visit with a shaman, who called his plan “idiotic,” helped him realize that in spiritual terms, he was closer to a goat.

The plan changed.

So he visited Buttercups Sanctuary for Goats, “the United Kingdom’s (if not the world’s) only sanctuary for abused goats,” and its head, “Britain’s foremost goat behavior expert,” Dr. Alan McElligott.

Thwaites learned, to his dismay, that goats do feel stress, especially since they are prey animals; that they’re smart enough to fake a limp when being led somewhere they don’t want to go; and that they “generally hang out in sex-segregated groups, and each group has a well-defined linear hierarchy.” This last part led to an uncomfortable question.

“I assume you’re going to be a male goat?” said Dr. McElligott. “Because there are key sex differences.”

Thwaites had considered many aspects of goatdom in researching this project. The possibility of having sex with the animal was not one of them.

“From a Darwinian perspective, sex is the whole point of animal life,” he writes. “However, I am sure my girlfriend would be extremely upset if she were cuckolded by a goat.”

Despite his realization that having sex with a goat would mean success for his project — reasoning, “I will only have had sex with a goat if I wanted to have sex with a goat, and [that will only have happened] if I have managed to adopt the mindset of a goat” — he avoided this awkward possibility by postponing his goat-change until after August, the goats’ rutting season.

(Fun fact: Since female goats are attracted to male goats by the smell, the males “pee onto their own goaty beards to increase the force of the smell . . . [and] make themselves more attractive to females.”)

After research, including embarrassing conversations with specialists, he constructed a goat outfit. He found doctors who work with prosthetics to help him construct legs that gave him a quadruped form, and placed 60 percent of his walking weight on his front limbs, which is how a goat walks. He made hinged arms that extended his forelimbs, wore a waterproof jacket made by his mother, and donned a helmet and chest protector, in case any goats should decide to head-butt him.

There was also — since digesting grass for nutrition, as goats do, is impossible for humans — an artificial stomach of sorts that, he decided as a compromise, he would spit chewed grass into, so he could heat the grass later in a pressure cooker to eat.

(If at this point Thwaites’ quest to transform himself into a goat seems to be going a bit far, it should be noted that his last project, 2012’s “The Toaster Project,” found him assembling a toaster completely from scratch, which entailed spending 250 times what a toaster costs and traveling two thousand miles to secure, and sometimes create, the parts. Malaise aside, he has an inclination for such projects.)

His costume assembled, Thwaites was ready. He contacted a goat farm in Switzerland, and the farmers agreed to let him visit and stay. He didn’t tell them his real purpose until he arrived, but when he did, they were willing to play along. His project would last six days: by night, he would sleep in a barn (like a human) with the goats but on a separate level; by day, he would live as a goat.

His first morning, Twaites was up at 4 a.m., when his hosts would milk their herd of 60 animals. Afterwards, they would be taking the goats down the mountain. Thwaites, since he was smaller and slower than the average goat, was given a head start.

That’s when he discovered the difficulty of walking in a fake goat outfit, especially downhill.

“I very quickly discover that walking downhill on four legs is extremely difficult. I stumble down the slope toward the barn . . . my front legs slipping from under me on the wet stone.”

Rita, one of the farmers, witnessed this amusing spectacle.

“Very good — ha, ha, ha, ho, ho, ho. But they go fast, Thomas. You shouldn’t wait. They’re very quick down the rocky path, maybe dangerous for you if you’re in the way.”

Getting down a steep, jagged mountain, basically walking on his hands, feels like “doing one-arm press-ups down the side of a mountain.”

Soon, he achieved his goal — and realized his fear — as the herd tramped down the mountain and were beside him.

“The first of the herd I aspire to join makes a break to get past me, then slows to a trot,” he writes. “Another passes at a fast trot, followed by another, and another . . . The reaction of the goats to me isn’t all that encouraging.”

Later, when another farmer drops by with his herd, Thwaites asks if he can try again.

This time, he joins the herd by a patch of grass, grazing for about five minutes, then ambling along to a different patch. He found that “the blue-green patches of grass are bitter, whereas the greener-green grass is sweet and much preferable.”

As he settles into this routine, the goats begin to regard him as one of their own.

“A couple come over to check me out, sniffing at my face,” he writes. “I try and sniff back, ignoring my human physical aversion to the powerful smell of their breath, a deep odor of fermenting grass, like distilled farmer’s silage. Though a few seem a bit scared at first, once they see me enjoying the grass like them, they stop avoiding me.”

As this happens, he makes a friend — a goat he knew only as number 18.

“Goat number 18 is a goat I seem to spend most of my day wandering around with. It’s kind of nice: I wander after her when she moves to another patch of grass, and likewise when I move off, she’s not far behind.”

Throughout this, however, Thwaites has learned that he has a far easier time walking uphill than down. This creates an issue, as he finds himself higher on the hill than the rest of the herd. As he looks down, he realizes that the herd is staring at him, hard.

“It’s suddenly gotten very quiet,” he writes. “Everyone’s stopped chewing.”

In the book, Thwaites compares the moment to the point in a Western when a stranger first enters a saloon.

“I remember reading that being the highest up in a herd can be a display of dominance. I think I may have just challenged the dominance hierarchy without realizing it. Oops.”

As he plans the possibility of having to “give a pretty good right hook with my prosthetic front leg,” then realizes he should be considering a head-butt instead, goat number 18 begins to wander. Now, with a herd member moving again, the other goats do the same. The situation is defused, and all return to eating their grass.

By the end of the day, the combination of rain and sweat made goat life less glamorous than Thwaites had hoped, and he longed for the comfort of a warm fire. So he removed his goat suit, and built a campfire to heat up the grass he’d been chewing on all day.

Once warmed, he tested it with a chemical solution to ensure it had broken down into sugar, then prepared to dine like a goat — which, as it happens, tastes awful if you’re not one.

“I tuck into the most unappetizing meal of my life: burnt grass stew,” he writes. “It doesn’t taste particularly sweet. Nor does it seem to me particularly nutritious.”

After, he returned to the farm, where his hosts served him a delicious pot of goat stew. What Thwaites found, in the end, was that life as a human goat was not all it was cracked up to be.

When his host Sepp — a goat farmer who spends his life in tranquility, virtually isolated from civilization on a mountaintop with just his wife, a farmhand and his goats — remarks that Thwaites is crazy because he lives in a city, and that “up here you wouldn’t need such a crazy idea,” Thwaites takes this to heart.

“If becoming a goat is about leading a simple life,” writes Thwaites, who is now in the UK researching a new project about the future of work, “perhaps a simpler way would be to become a goat farmer rather than a goat.”