I wish to express my thanks to a number of persons who helped to make this book possible.

First, I wish to thank Leo, wherever he may be, for his devoted interest, skill and determination in carrying out this very important work under stressful conditions, guided by his faith and confidence in the value of what he was doing. My wife Jean and I are most grateful for the patience and care that he took to communicate to us his knowledge and experience.

I am also grateful to those who participated in Leo's program, making this work possible, and particularly to those who shared in detail the experiences that they underwent and the results that followed. I also thank Leo's family and supporters who aided him in carrying out his work.

I wish to thank Ann and Sasha Shulgin for pointing out to me the importance of getting Jacob's efforts recorded.

My thanks to Terence McKenna for permission to use his title for this book.

I am extremely indebted to Rick Doblin, Sylvia Thyssen, Brandy Doyle and MAPS for their assistance in the editing and completion of the manuscript, and for taking the steps to have the manuscript published.

I wish to thank my wife Jean for her assistance and loving support throughout all stages of this project, from the initial interviews to the completion of the final manuscript.