The Mory’s cup that was present at the founding of the Whiffenpoofs in 1909 is coming back to Yale.

Kept by the family of one of the five original Whiffs, who first gathered at Mory’s to sing and drink in January 1909, the founding cup will pass through the hands of eight decades of Whiffs — from members of the 1930s to the present — accompanied by the familiar strains of the Whiffenpoof Song this weekend.

Over 600 bow-tied, white-gloved Yale Whiffenpoofs will descend on campus today to celebrate the Whiffs’ 100th year. Beginning with a forum on the history of a cappella Friday and ending with a memorial service for recently deceased Whiff alumni on Sunday, the centennial weekend will be awash in the traditions of the oldest a cappella group in America.

“Being able to meet people who have been through the Whiffs in all sorts of different eras and seeing how that experience was different for them is going to be really cool,” said Brendan Dill ’10, a current Whiffenpoof. “It’s going to be an invasion.”

An invasion, indeed. This afternoon, 40 different groups of Whiffs past and present are taking over rehearsal rooms around campus to prepare for a three-hour public concert in Woolsey Hall beginning at 7:30 p.m. Each class of singers will perform two songs in what Whiffenpoof Alumni Association President Dennis Cross ’65 called “a marathon.” Even the oldest Whiff at the event, Stowe Phelps ’39, will sing.

Mike Lavigne ’10 said the 2010 class of Whiffenpoofs will conclude the concert with three songs: “Nature Boy,” arranged by the current Whiffenpoofs, “Too Young to Say Goodbye,” a reunion song dedicated to the memory of a recently-deceased Whiff, and, of course, the time-honored Whiffenpoof Song, which all the alumni sing and which traditionally brings every Whiffenpoof concert to an end.

“We’ll stand up wherever we are in Woolsey Hall to grab hands as best we’re able, and sing,” said Barry McMurtrey ’88, who helped coordinate the centennial reunion and curated an exhibit of Whiffenpoof memorabilia in Sterling Memorial Library.

Any member of the Yale community can attend the concert, though the singing won’t stop after the concert’s close.

Over the rest of the weekend, small groups of Whiffenpoofs plan to find corners, common rooms and courtyards where they can burst into song, McMurtrey said. Some alumni will also relive their undergraduate days by eating dinner in the residential college dining halls tonight.

One place the Whiffenpoofs will not be singing is in their beloved birthplace, Mory’s. Despite the efforts of the Whiffenpoofs and other alumni to revive the eating club, it was unable to re-open in time for the centennial this year. The loss was disappointing, McMurtrey said.

“It is a stunning reminder of our mortality,” he added.

All 600 or more Whiffenpoofs, as well as their families, will mingle at a tailgate before the Yale-Lafayette football game Saturday afternoon. Whiffenpoofs who attend the game will run onto the field during halftime, accompanied by the Yale Precision Marching Band.

Reconvening in Sterling Memorial Library later Saturday afternoon for a cocktail party, the Whiffs plan to parade from the library, carrying ceremonial banners, cups and maces, to Commons for a festive banquet that lasts into the “wee hours” of the morning, McMurtrey said.

And there will, of course, be more singing.

“All of the Whiffs getting together again and singing for their peers, this is what they love to do,” Cross said. “That’s the essence of the reunion.”

For the current class of Whiffs, who have only sung together for a month and a half, the reunion is a chance to learn about the 100-year-old tradition they joined only recently.

“Seeing these guys who are getting along in their years gives you a sense of the magnitude of what we do here,” Lavigne said. “Anything we do here really carries over for the rest of our lives.”