Yes, WYSIWYG, I do know that. In fact, Sam Charters, who was the first folk researcher to find Blind Willie Johnson's home (a couple of years after he died) found dozens of old Gospel song books dating from about 1880 to the 1920s. Johnson had used them as a resource. Some of his versions were more origonal than others, but almost all had roots in traditional Christian music.

The exact versions that became "common coin" in Blues and Folk circles in the 1950s-1960s were Johnson's, and I feel that he did not receive proper credit, even from those who knew better. (BTW, he was blind, so how did he read all those old hymnals? Just curious.)