Henry Slade

According to Readers Guide to The Mahatma Letters to A. P. Sinnett:

Slade, Dr. Henry, an American medium of exceptional talents. He was thoroughly tested by HPB and HSO and was picked by HSO and others to go to Russia for scientific tests of his phenomena. At one time he gave special courses to professors of Leipzig University in Gemany, and as a result Prof. Zollner published a book Transcendental Physics in which he challenged the world to account for Slade's phenomena save by a "spiritual" hypothesis. The book was translated into English by C. C. Massey ... See bibliography HPB I: 525; ML index; ODL I: 201; SH, pp. 13, 18, 74, 166.