In portrait photography of the 1860s exposure times took how long

I know that for the very earliest daguerrotypes could had an exposure time of 5 minutes -- a very long time!  But that time was reduced as the process improved.  Depending on lighting and conditions, exposure times could be a short as several seconds.

By the way, those early photographic processes were called daguerrotypes after the inventor, Louis-Jacques-Mandé Daguerre, who introduced his form of photography in 1839.  By 1860, other types of processes had also been invented and became more common in usage.