Robert McKim predates ALL the writers and Proponents of the Visual Thinking Concept, making him the "grand daddy" of it all in a certain respect. It's this book I've taken into Boeing and it's this information that I look to when I'm trying to get to the core of what being a visualizer is all about.
This book is one of the earliest clear descriptions describing how to "do" visual thinking, thus serves as one of my key sources in my personal promotion of the "visualizer" concept in the technical arena where I work.