Thousands including families with children flowed over bridges across the Nile into Tahrir Square, a sign that they were not intimidated after the protesters fended off everything thrown at them by pro-Mubarak attackers -- storms of hurled concrete, metal rebar and firebombs, fighters on horses and camels and automatic gunfire barrages. The protesters passed through a series of beefed-up checkpoints by the military and the protesters themselves guarding the square.
The crowd, which appeared to approach 100,000, was the biggest since Tuesday, when a quarter-million turned out. A man sitting in a wheelchair was lifted -- wheelchair and all -- over the heads of the crowd and he pumped his arms in the air. Thousands prostrated in noon prayers and immediately after uttering the prayer's concluding "God's peace and blessings be upon you," they began chanting their message to Mubarak: "Leave! Leave! Leave!"
In the afternoon, a group of Mubarak supporters gathered in a square several blocks away and tried to move on Tahrir, banging with sticks on metal fences to raise an intimidating clamor. But protesters throwing rocks pushed them back.
The Arabic news network Al-Jazeera said a "gang of thugs" stormed its offices in continuation of attacks on journalists by regime supporters that erupted Thursday. It said the attackers burned the office and damaged equipement. The editor of the Muslim Brotherhood's website, Abdel-Galil el-Sharnoubi, told the AP that policemen stormed its office Friday morning and arrested 10 to 15 of its journalists. Also clashes with sticks and fists between pro- and anti-governemnt demonstrators erupted in two towns in southern Egypt.
More detailed scenarios were beginning to emerge for a transition to democratic rule after Mubarak's nearly 30-year authoritarian reign.
Proposals floated by the Americans, the regime and the protesters share some common ground, but with one elephant-sized difference: The protesters say nothing can be done before Mubarak leaves, while the 82-year-old president insists he will serve out the remaining seven months of his term to oversee the transition process. Protesters labeled their rally the "day of leaving," a reference to their demand Mubarak go on Friday. Some held up signs reading, "Now!"
"You don't understand the Egyptian culture and what would happen if I step down now," Mubarak said he told President Barack Obama. Mubarak warned in an interview with ABC News that chaos would ensue.
But the Obama administration was in talks with top Egyptian officials about the possibility of Mubarak immediately resigning and handing over a military-backed transitional government headed by Vice President Omar Suleiman.
Such a government would prepare the country for free and fair elections later this year, according to U.S. officials speaking on condition of anonymity to discuss the continuing sensitive talks. The officials stressed that the United States isn't seeking to impose a solution on Egypt but said the administration had made a judgment that Mubarak has to go soon if there is to be a peaceful resolution.
Suleiman has offered negotiations with all political forces, including the protest leaders and regime's top foe the Muslim Brotherhood, over constitutional changes needed to ensure a free vote ahead of September presidential elections to replace Mubarak, who has promised not to run again.
Among them: provisions to ensure independent supervision of elections, a loosening of now suffocating restrictions on who can run for president and a term limit for the president.
Nobel Peace laureate Mohamed ElBaradei, one of the leaders of the protest movement, lay out his scenario on Friday: a transitional government headed by a presidential council of two or three figures, including a military representative. He suggested that Suleiman -- a military man who was intelligence chief until being elevated to vice president last week -- was an acceptable figure to sit on a presidential council, saying he respects Suleiman.
While "a lot of people see him as part of the Mubarak regime .. these are issues that could be sorted out," ElBaradei said. Several organizers in Tahrir said they were willing to see Suleiman head any transitional government.
But ElBaradei repeated the protesters' consistent condition that Mubarak must leave immediately before there can be negotiations with the government over the nation's future.
"He should hear the clear voice coming from the people and leave in dignity," ElBaradei told a press conference. "The quicker he leaves in dignity the better it is for everybody."
There were other potential difference with Suleiman's scenario. ElBaradei said the constitutional changes must include greater freedom to form political parties, which now effectively need the approval of Mubarak's ruling party. Protesters also demand the lifting of the emergency law in place for the entirety of Mubarak's rule, giving security forces near unlimited powers.
Suleiman has mentioned neither issue, though he said the regime is willing to discuss far-reaching changes.
Another issue is timeframe. Suleiman spoke of completing constitutional changes by July to hold presidential elections in September. ElBaradei said that was not enough time to uproot a system that has ruled for decades through a monopoly on politics and widespread election fraud to ensure a proper vote.
"People are not stupid not to understand that this is not really a genuine desire to go for reform," he said of the July/September schedule.
Instead, he said, the presidential council should rule for a year under a temporary constitution, during which time a permanent document would be drawn up and only afterwards elections held.
One self-professed potential candidate -- Arab League chief Amr Moussa -- appeared in the square Friday, his convoy greeted by chants of "we want you as president, we want you as president." Moussa, previously a former foreign minister under Mubarak, has an elder statesman appeal for some Egyptians, boosted by the tough rhetoric he takes on Israel.
Asked earlier by France's Europe 1 radio if he would consider a role in the transitional government or eventually running for president, Moussa replied, "Why say no?"
Another visitor to the square Friday: Egyptian Defense Minister Hussein Tantawi, who mingled with protesters and held friendly but heated discussions, telling them most of their demands have been met and they should go home. he was the highest level government figure to visit the square in more than 10 days of demonstrations.
At Tahrir, soldiers checked IDs to ensure those entering were not police in civilian clothes or ruling party members and performed body searches at the square's entrances, a sign that Egypt's most powerful institution was sanctioning the demonstration.
The atmosphere was peaceful after the 48 hours of violence between pro- and anti-Mubarak crowds battling with rains of rock and concrete torn from the street and shields fashioned out of sheet metal from a construction site. At least eight people were killed in the fighting and more than 800 injured. Gangs backing Mubarak attacked journalists and human rights activists across Cairo Thursday, while others were detained by soldiers.
The pro-Mubarak crowds that have attacked demonstrators and foreign journalists did not have a visible presence in Tahrir on Friday. On the other side of Cairo, dozens of regime supporters carrying machetes and sticks set up an impromptu checkpoint on the ring-road highway encircling the city of 18 million, stopping cars to inspect them and ask for IDs. The roadblock appeared to be looking for protesters heading to Tahrir. One of the armed men wore a sign around his neck reading, "We are sorry, Mr. President."
In Tahrir, protesters formed their own cordon inside the military's to perform a secondary check of IDs and bags. Many of those arriving brought fresh bread, water, fruit and other supplies, and the atmosphere was relaxed. Long lines formed at tables of people handing out tea and bread. Many waved the Egyptian flag or chatted amicably with the soldiers. Women in full face veils and enveloping robes stood close to women in blue jeans and tight tops.
Around the square were makeshift clinics, set up in the entranceways of stores, including a KFC. At one, a man received an injection in his arm. Above another was the sign of an interlocking crescent and cross.
Around 5,000 of the protesters prostrated themselves in prayer at noon. Though men and women prayed separately as is traditional, the women knelt in a block parallel to the men instead of behind them out of sight or in a separate area entirely as takes place in most Egyptian mosques. After uttering the concluding "God's peace and blessings be upon you" of the prayer, they began the chant: "Leave! Leave! Leave!"
A number of celebrities of Egyptian cinema and TV joined the march, including Sherihan, a beloved screen beauty from the 1980s and early 1990s who largely disappeared from the public eye because of health issues. "This is really a popular revolution, it's civilized and honorable," she told Al-Jazeera TV.
"We're calling on this to be the largest protest ever," said Mahmoud Salem, a youth activist and blogger. "We are hoping it will be the last one." He said that during Thursday's turmoil, his car was attacked by regime supporters as he and four friends tried to deliver supplies to the square. He said the rioters relentlessly smashed the car windows and ripping off the side mirrors until he and his colleagues fled from the car.
"It was like a zombie movie," he said.
AP correspondent Maggie Michael contributed to this report.