The Master Key

"In no branch of human knowledge has there been a more lively increase of the spirit of research during the past few years than in the study of Psychology, Concentration and Mental Discipline. Many points of "mental doctrine" have been passing afresh through the crucible; plain instruction is a popular cry, and, in some directions, a real requirement of the age; the requests for authentic lessons in Thought Control, Mental Discipline and Concentration have never before been so great as in recent years."-From the Preface.