A correspondence from Mrs T. B. Cranz printed in the August 17th, 1872 edition of Banner of Light endorsing spirit photographer William H. Mumler and slate medium Dr. Slade.
Cranz states she went to the slate medium and received a message from her deceased relatives. The slates directed her to go to Mr. Mumler so that they could reveal themselves. After sitting with Mumler she recognized two of the spirits in the photograph which she stated were “proofs of spirit communication”.