So families brought children, people shared pastries and dried dates, everyone took everyone else's picture.
Even deep into the evening, a dwindling crowd remained, joined in derision as Mubarak announced that he would not be seeking reelection. "We demand his ouster and his sentencing," said Mahmoud Ibrahim, while others waved shoes in the air, a traditional Arab sign of disrespect.
Behind the long day's exhilaration was a sense of free will under a careful and tentative test. Some in the crowd realized that they were on the verge of throwing off more than the shackles of a 30-year autocratic regime; this was a personal moment, too.
"They are thinking about us as nothing," said Abd al-Rahman, a 24-year-old English teacher, referring to the men around Mubarak. "But we have to change ourselves. It's not about Mubarak. It's about the whole culture. Everything."
From the earliest school years, he said, "They are putting our minds in chains." The teacher is god; the professor is god; the boss is god; the president is god. "Well, where is the space I need" - pointing at his own chest - "to make a new thing?"
He looked around. Here in Tahrir Square was the space. And something new was being made.
For Rahman it's about the freedom to ask questions. For others, it's about self-respect.
"I am not poor," Hatem el-Said said. "I have a lot of money. I own my own business. But I see people who can't afford to eat more than one meal a day. I can't accept that any longer."
He went to college in New York - "It doesn't matter which one," he said - and he learned to love American values, even as he believes that America itself has lost faith in those values, at home and especially abroad. But if America at least aspires to dignity and freedom and the pursuit of happiness, why, he asked, can't Egypt do the same?
He feels no fear now. "What's the worst that can happen? I'd rather lose my life than go on living this way," he said.
Azzam, who runs a consulting company that specializes in oil and gas engineering and in food products, said he lives in a good neighborhood and sends his children to the best schools. "But we have our personal pride," he said. That's why he came out Tuesday. It's time, finally, he said, for an Egyptian democracy - a democracy grounded in Egyptian culture and religion as well as politics.
"The way we implement democracy here will be different," he said, "but it will be democracy."
A stiff breeze came up in the afternoon, whipping the thousands of Egyptian flags and homemade signs carried by demonstrators. One sign, directed at Mubarak, said: "Feeling is a gift. Don't you have this gift?"
Over the past week, this square had at times seen violent clashes between protesters and police. But Tuesday, the crowd surged good-naturedly this way and that. Spontaneous call-and-response chants would ignite in one corner or another. Effigies of Mubarak were hanging from street lamps, but they didn't really reflect the mood, and people paid them little mind. At the prescribed hours of Muslim prayer, many knelt down, while others stood in respectful silence. Then the hoopla would set in again.
"This is a revolutionary wave," said Amir Shalan, who worked for an Islamic television station here before the government shut it down. "This revolution will change the Middle East if it succeeds."
In what ways? Hassan Nour el-Din, who studied archeology but makes a living as a tour guide, ticked off the ills that revolution can address: Poverty. Brutality. Ignorance. Illiteracy. Disease.
Seemingly everyone here was speaking of the Mubarak regime in the past tense. "We consider him banished already," Azzam said. The fear wasn't that he will hold on to power - but that he will "return" to power.
Although those gathered here might fear that Mubarak could some day reclaim his place, for them, there was no going back. The spirit of inquiry, the sense of self-respect, the assumption of personal responsibility are things that Egyptians think will endure.