The potion smelled like fermenting fruit; it was sniffed and handed cautiously around in the mosquito-thick twilight. It was ayahuasca, a powerful, centuries-old psychedelic drug made from vines and ingested regularly by the local shaman, or medicine man.
Barefoot and clad in a grass skirt, the shaman lit a cigarette of coarse-tasting tobacco. Then, in a spiritual healing ritual that was surely a first for the visitors, he slowly made his way around the palm-thatched hut, brushing their heads and shoulders with the smoke and chanting softly.
He is 39, has three apprentices, and drinks the vision-inducing ayahuasca to diagnose and treat an array of ailments, he explained later. He sees one or two patients a week, taking payment in fish, bananas or pigs.
Close to 60 different tribes inhabit Peru's rain forest, drawn from 18 indigenous groups, and most still share a strong spiritual life rooted in traditional beliefs.
On this trip, there were other glimpses of a delicate indigenous culture facing an uncertain future.
In the adjacent village of Monte Alegre, the tourists visited an open-air elementary school, donating school supplies, soccer balls and toothbrushes, then joining the delighted youngsters in a raucous song and dance.
Lunch followed: Wild boar, catfish and a chicken-rice dish were cooked in palm leaves and eaten with the fingers as guests sat on the floor.
The visitors also paddled dug-out canoes, a staple on the network of tributaries that feed the Amazon.
In general they were greeted warmly as they shopped for handicrafts and wandered around.
That's not always the case. There still remain about 15 small "no-contact" tribes in Peru, essentially untouched by the 21st century, and intrusions by outsiders have on occasion stirred friction.
Change is unmistakably on the horizon in this remote region.
The Amazon rain forest covers 60 per cent of Peru, but only 5 per cent of the country's 30 million people live here, and most remain very poor, dependent on fishing and subsistence farming, even as Peru's strong national economy makes it a Latin American star. And while oil prospecting and logging are shrinking the rain forest, so too are demographic migratory patterns.
In the fish-market town of Nauta, for instance, perched on the edge of the Pacaya Samiria reserve with a population of 29,000, electricity and a paved-road connection to Iquitos have redefined life in the past decade.
Exposing that vulnerable lifestyle to hordes of tourists thus entails navigating a fine line.
Monte Alegre had just one previous visit by foreigners, and it would be a while till there was another. En route back to the tour ship, G Adventures guide Victor Coelho stopped in a different village, to see if there was interest in arranging something similar.
"What we don't want to do," he said, "is create a culture of dependency."
Timothy Appleby is a former Globe and Mail foreign correspondent and crime reporter. He travelled courtesy of G Adventures, which did not read or approve this story