For some reason, anything connected to Charles Cullis in terms of autographs and ephemera seems especially difficult to come by. 

The present is a c.1890 envelope to Mary Floyd Cushman entirely in the hand of Dr. Charles Cullis, pioneer of the Divine Healing movement in America. He was a medical doctor who was on the Board of what is now the Boston University School of Medicine, but who also saw this as working in tandem with miraculous healings and a more holistic approach to care. He was probably the most nuanced of the voices in a loosely associated movement that contained more radical figures like R. Kelso Carter, John Alexander Dowie, etc. 

The envelope is likely to Mary Floyd Cushman the elder, aunt of the famed medical missionary to Angola of the same name. 

Ephemeral to be sure, but from an important figure of whom few scraps seem to have survived.