The Feb. 2 attack on the protesters came during an 18-day uprising that forced Mubarak to step down Feb. 11.
The assault, carried live on regional television channels, provided what protesters took to be solid proof that Mubarak's regime was desperate and on the brink of collapse. The initial attack sent protesters at Cairo's Tahrir Square, the epicenter of Egypt's revolution, running from the assailants, who had whips and swords. But many protesters later found the courage to pounce on the attackers, wrestling them to the ground before beating them.
Feb. 2 was among the most violent days of the uprising, with protesters and Mubarak loyalists fighting it out at Tahrir Square and adjacent streets with rocks, firebombs, and slabs of concrete. The fighting lasted well into the night. At least three people were killed and 600 wounded.
The horse-and-camel charge has become known as "the Battle of the Camel."
The two speakers charged, Fathi Surour and Safwat el-Sharif, face separate charges of corruption and are expected to stand trial on those, too.
Mubarak, 83, is scheduled to be tried next month for ordering the use of deadly force against the protesters. More than 800 protesters are believed to have been killed in the uprising.
Huge protests are planned for Friday to demand justice for the revolution's victims as well as measures to purge former regime officials from political and economic life. The Muslim Brotherhood, Egypt's most organized political movement, has said it will join the pro-democracy demonstrators at Tahrir Square for the so-called Friday of Accountability.