Over 120 curious uptown residents gathered last week to take part in a brief but highly-anticipated political experiment: They began deciding how to spend a sliver of the city budget in their own neighborhood.

At the first-ever participatory budget assembly in East Harlem, held at a local food pantry, City Council member Melissa Mark-Viverito committed at least $1 million to programs and projects suggested and approved by her constituents.

The scheme arguably represents direct democracy in its purest form.

“Only four out of 51 council members are engaging with this initiative,” said Mark-Viverito, who showed up at the Yorkville Common Pantry to introduce and support the process. “We’re here making history in many ways.”

The other three council members trying out participatory budgeting represent Brooklyn and Queens. Mark-Viverito is the only Manhattan member involved, in a pilot that could be expanded and repeated if it works well.

Over the next six months, participants will identify and debate possible infrastructure projects at a series of neighborhood assemblies. They’ll use the city’s capital budget, reserved mostly for the construction or improvement of structures and spaces, like parks and firehouses.

Constituents can’t , however, access the city’s expense budget, which pays for daily operating costs, including public employees’ salaries.

Some participants then volunteer to become budget delegates who will refine the assemblies’ rough proposals. Budget delegates will meet in committees from November until February to develop these suggestions into concrete, costed-out projects.

Finally, the proposals face a community vote in March. Although all citizens over 16 who live, work, or own a business in Mark-Viverito’s district, or have children attending schools there, can become budget delegates, only residents over 18 can vote on final proposals.

“We want to include those who don’t usually participate politically, no matter your demographic,” announced George Sarkissian, district manager of Community Board 11, at the first assembly. It offered Chinese translation, a nod to East Harlem’s growing Chinese population; the next six assemblies, including two aimed at youth and seniors, will offer Spanish translation.

The first meeting drew a swarm of participants and observers: East Harlem residents, social science researchers, reporters and community activists.

After Sarkissian explained the scheme, the audience formed smaller groups, debated various infrastructure projects and eventually voted on three proposals to present at the end of the evening. Facilitators guided the discussions.

Sociology researchers observed throughout the evening. “I’m here to research how to apply crowdsourcing techniques to the participatory political process,” explained Sean Ansanelli, a graduate student in urban planning at Columbia University.

Eligible projects must cost at least $35,000, remain useful for a minimum of five years and involve a physical public improvement. Among the evening’s proposals: a youth center, a shelter for single women and equipment for an East Harlem computer lab.

Organizers and facilitators were quick to point out that smaller projects, like fixing sidewalks or deploying more trash cans, were perhaps more realistic given the $1 million spending limit.

“I think the community wants larger projects, and finds it hard to think of more modest proposals or microprojects,” said facilitator Tricia Taylor, a graduate student in clinical social work at Hunter College.

A “City Budget 101” guide distributed at the assembly estimated the city’s average capital budget at $9.5 billion a year between 2010 and 2013. The neighborhood’s $1 million represents a tiny fraction of that, far less than 0.1 percent.

Nonetheless, $1 million represents a significant proportion of the average $2 million to $9 million annually allocated each City Council member in discretionary funds. The money at stake here will come from Mark-Viverito’s annual discretionary fund for capital projects.

“This is giving people a sense of agency, and control over what is done in their communities,” Taylor added. “It’s exciting. Particularly in this community, which is changing a lot and very quickly, original longtime residents need their voices heard more than ever.”

Mari Dipuma, a 42-year-old educator and participant, had a similarly upbeat take. “I appreciate this because now we have a say,” she said. “That is real democracy. I’m also happy that my opinions are heard, and that the community’s opinions are heard.”

But Krystle Cox, a 27-year-old administrative school assistant, had some complaints. “The discussions were good, but I feel they could’ve been better,” she said. “I wish there had been more people in our group.” But, she added, “I’ll attend future meetings and see what happens.”

In fact, Cox volunteered to become a budget delegate. “I want this country to change for the better, and you personally have to be the change you want to see,” she explained. “I can’t say that I wish for things to change, and yet do nothing myself.”

Questioned the next day, Mark-Viverito said she felt disappointed at criticism over poor attendance.

“It’s difficult to really get people to participate,” she said. “This isn’t from a lack of desire on their part, but from a deep cynicism. East Harlem is often an ignored, disenfranchised and poor population, and the government isn’t engaging them.”

Still, she remained optimistic about the new process. “I think the movement will grow, and give people real faith that government can play more of a role in their lives,” she said.

Proposals that emerge from the participatory budget process will be published online at http://pbnyc.org.