The diagrams in this book are based on spacetime diagrams, which are 2-D diagrams where the horizontal dimension represents space and the vertical dimension represents time (the future is up). All events within spacetime are volumes that have both a spatial and a temporal extent.
The vertical lines are called worldlines: they represent the course of a particular object (or world) in spacetime. In this work, a worldline is used to represent the 4-D body of an observer (multiple worldlines can be used to represent a 5-D body). The grey cones intersecting in the middle of the figure locate the here and now at the center of the diagram (in physics, they also represent light cones). The small spheres throughout the graph represent various events (for simplicity, their worldlines are omitted).
There are at least two objects in the figure which are not present in traditional spacetime diagrams: mind and emotion (both of which are only illustrated only at the here-and-now, since representing emotions and mind throughout the body’s worldlines would make the diagram overly complex). The mind is represented by the referential arrows centered at the subjective origin. Emotion is represented by the torus in the same location. There is not too much significance to the fact that it is a torus, but I like that it connotes both fusion reactors and donuts (I am a big fan of the Simpsons).