Lawrence Spagnola, who co-authored King's 2012 book "The Riot Within: My Journey from Rebellion to Redemption," sat with family members at both services.
The family can be proud of the "amazing degree of grace and wisdom" with which King carried himself after being violently thrust into the media spotlight, Spagnola said.
King's death is being treated as an accidental drowning but authorities are awaiting autopsy results to determine the official cause of death.
He became famous after his beating by Los Angeles police in 1991 was captured on videotape and broadcast worldwide, as were photos of his bloodied and bruised face.
The images of the grainy video became a national symbol of police brutality. It was played over and over for the following year, inflaming racial tensions across the country.
More than a year later, four officers charged with felony assault in the beating were acquitted by a jury with no black members. The verdict sparked one of the most costly and deadly race riots in U.S. history.
During the unrest, which left more than 50 people dead and caused more than $1 billion in property damage, King famously pleaded for peace by asking, "Can we all get along?"
His famous words were embroidered on the lid of King's casket, next to a portrait of him.
"He never asked if people would remember Rodney King. But he wondered if they would remember those words," Spagnola said. "I told him, 'long after you're gone, your words are going to live.' And I think he took some solace in that."