History buffs. Civilian salute?

I have a question about the historical accuracy during the pass and review scene. During this scene there are two subjects,  one appears to be a Frederick Douglass, place their right hands over their hearts in lieu of a salute. 
How accurate is this? 
My research indicates that this tradition of having your hand over your heart really didn't come around until the 1940's after a salute that was similar to the fascist salute (Bellamy salute )fell out of favor.  There was another salute before that was known as the Balch salute that accompanied different Pledge of Allegiance. Both of these salutes were for school children and the earliest the Balch was used was after the Civil War.
Does anyone know what would have been the appropriate civilian response to the pass and review of the troops and the flag?
Thank you