VATICAN CITY — The Vatican summoned cardinals to the Holy See on Friday to begin preparations for electing the new leader of the Catholic Church, a day after Benedict XVI resigned to a life of seclusion.

Angelo Sodano, dean of the College of Cardinals, set the first General Congregation of Cardinals for Monday at 9:30 a.m. A second meeting is scheduled for 5 p.m. the same day.

Benedict ended his papacy at 8 p.m. Thursday, claiming that at 85, he was too frail to continue in office.

He retired to Castel Gandolfo, on the outskirts of Rome, and will not return to the Vatican until a new pope is elected.

Vatican spokesman Federico Lombardi said Benedict had “slept very well” after becoming the first pope in almost 600 years to resign from his post.

Benedict watched news broadcasts about his resignation on television, which “he appreciated very much,” and after dinner went for “a little walk” in the corridors of the papal palace in Castel Gandolfo, Lombardi said.

On Friday he celebrated Mass at 7 a.m. In the coming days, in addition to praying and studying, the former pope also planned to “play a bit of piano in the evening,” Lombardi added.

As he left the Vatican, the “pope emeritus” took with him books on theology, spirituality and history, as well as some music records, the spokesman said.

Cardinals from around the world already have begun arriving for next week’s General Congregation, a forum for preliminary discussions that may last several days.

Once ready, cardinals will set a date for the start of the conclave, the closed-door assembly held in the Sistine Chapel tasked with electing a new pope.

Lombardi said not to expect news about the conclave to emerge on Monday. “A decision is not foreseeable” on that day, he said.