R.C. Douglass wrote a series of 13 installments in Unity magazine from March 1913 to March 1914 entitled Metaphysical Bible Dictionary. These installments were published as a book in August 1914. He is important because Unity published its own Metaphysical bible Dictionary in 1930.
The photograph of R.C. Douglass is from Supplement to Unity, May 15th, 1898, vol. 10, no. 10. Published by Unity Tract Society, 509 Hall Building, Kansas City, MO.
According to an obituary on FindAGrave, Rufus Collins Douglass was born 8 Mar 1837 at Dover-Foxcroft, Piscataquis County, Maine and died 1922. Burial at Oak Grove Cemetery, La Crosse, La Crosse County, Wisconsin. Married to Sarah E Weston Douglass (1844–1897) (m. 1865), one child: Reuel Elmer Douglass (1874–1876). https://www.findagrave.com/memorial/98343309/rufus-collins-douglass
Catalog of Copyright entries for RC Douglass' book Spiritual Evolution or Regeneration has a daughter Alice D. Anderson as his daughter.