WASHINGTON — How do you get ready to serve as jurors weighing whether a president should be removed from office? Senators have just four days left to find out.

Technically, President Donald Trump's trial has already reached the chamber: Members sat through the preliminary proceedings on Thursday when they officially received the two articles of impeachment from the seven House managers and heard them read aloud by lead manager, House Intelligence Committee Adam Schiff, D-Calif. They were all sworn in by Chief Justice John Roberts, who will preside over the trial, which is expected to kick off in earnest with opening arguments on Tuesday.

Some members are spending the final weekend diving into background material.

Sen. Robert Menendez, D-N.J., ranking member of the Senate Foreign Relations Committee, said that he took notes on the Senate floor Thursday as Schiff read the articles and plans to further review them as well as trial briefs before the trial begins next week.

“I'll get a copy of the [Congressional Record] to review them again and look at the various fine points of the elements of both articles of impeachment,” he said, adding that he plans to review the trial briefs that the House and White House counsel must deliver before Tuesday, which will outline their arguments.

Sen. Mike Braun, R-Ind., said that he’s been paying attention to the case from the get-go — but others, he said, might need to invest more time catching up on the details.

“For any of us who haven’t been preparing, they’re cramming right now,” he said. “I’d say it’s like a test back in college — you probably need to be prepared.”

Others have been looking even further into the past.

Sen. Debbie Stabenow, D-Mich., said that she’s been studying previous impeachments. “I've looked at the historical record, on actually every other impeachment that's gone on since the beginning — both presidents and judges and so on — to really understand” how the trial will work, she told NBC News.

Sen. Angus King, I-Maine, has been poring through the book "High Crimes and Misdemeanors" by Frank O. Bowman III, which explores the Clinton impeachment and impeachment’s historical beginnings. He has filled the book with highlighter and annotations in the margins and said he’s been thinking deeply about the origins of impeachment, including the first one in 1376 in England, and the Founders’ view of the importance of the process.

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King’s guiding principle, he said, dates to a quote from Sen. Howard Baker, R-Tenn., who in 1973, while serving on a Senate committee investigating the Watergate break-in, asked of President Richard Nixon: “What did the president know and when did he know it?”

King told NBC the question now is, “What did the president do and why did he do it?”

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Sen. Richard Blumenthal, D-Conn., said he had also read the Bowman book, calling it “fascinating.”

“I mean people were killed after they were impeached," under the old British system, he said. "So the history is pretty interesting."

Some senators have been reading a 43-page memo by former Sens. Russ Feingold, D-Wis., and Chuck Hagel, R-Neb., who both served as impeachment trial jurors in the Clinton impeachment. “What a Senator Should Know,” obtained by NBC News, summarizes the pair's experience and offers guidance, calling an impeachment vote the “most momentous decision a senator can make.”

Others are looking for assistance from beyond Capitol Hill. On his way out of the chamber Thursday after the Senate adjourned, Sen. Ben Cardin, D-Md., stopped at Senate Chaplain Barry Black: “Pray for us,” he said.

Sen. Tom Carper, D-Del., told NBC that a number of people have recently approached him saying “that they are praying for us.”

“I asked them to pray for wisdom for us, to have the knowledge on what is the right thing to do. And I asked them to pray that ... we would have the courage to do what we know to be right.”

Carper and others said that with the trial now just days away, the heaviness of the task was sinking in. “I was struck today by the ... sense of gravity, solemnity, in the chamber,” he said.

When the chief justice entered the chamber, you could “feel the weight of the moment,” Senate Minority Leader Chuck Schumer, D-N.Y., said.

“I saw members on both sides of the aisle visibly gulp. The weight of history sits on shoulders and produces sometimes results you never know will happen,” he told reporters.

Sen. Tim Scott, R-S.C. said, "This is a historic moment in history and as I prepare for the weight of the impeachment process, I’ve consulted an array of people, including friends in the faith community, members of my staff who were around for the 1999 impeachment trial, and legal professionals who have closely examined the evidence gathered in the House."

"One thing that I am mindful of is to prayerfully consider everything that is provided to the Senate instead of rushing to a conclusion," he said. "I trust the process and am looking forward to a swift ending.”

Most of Scott's GOP colleagues expressed frustration that the Senate was conducting any sort of trial.

“I feel like we're wasting a lot of time and a lot of energy," said Sen. Kevin Cramer, R-N.D. "And I wish we could be doing more productive things, but this is what we have to do at the moment so this is what we do — get paid the same no matter what.”

The trial requires the attendance of all sitting senators, including the four currently running for the Democratic presidential nomination — Michael Bennet of Colorado, Amy Klobuchar of Minnesota, Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts — who were all scheduled to spend the weekend in Iowa.

House managers, on the other hand, were expected to stay in Washington, according to one of the seven managers, House Judiciary Committee Chairman Jerry Nadler, D-N.Y., who declined to elaborate on how the group was preparing for the trial. Nadler served on the Judiciary Committee during the impeachment of President Bill Clinton.

Asked if he plans to watch the Senate’s trial of Clinton from 1999, he suggested that there’s no need to. “I lived it in real time,” he said.