The Art of Not Being Governed

"In one sense, the difficulty of moving grain long distances, compared with the relative ease of human pedestrian travel, captures the essential dilemma of Southeast Asian statecraft before the late nineteenth century.

...

Imagine a map constructed along these lines, designed to represent relative degrees of potential sovereignty and cultural influence. One way of visualizing how the friction of distance might work is to imagine yourself holding a rigid map on which altitudes were represented by the physical relief of the may itself. Further, let's imagine that the location of each rice-growing core is marked by a reservoir of red paint filled to the very brim. The size of the reservoir of paint would be proportional to the size of the wet-rice core and hence the population it might accommodate. Now visualize tilting this map...

The angle at which you had to tilt the map to reach particular areas would represent, very roughly, the degree of difficulty the state would face in trying to extend its control that far."

That's from the terrific The Art of Not Being Governed by James C. Scott, I'm working my way through it.