Belgian-born artist Francis Alys’s medium is walking. On one walk, he carried a can of paint with a tiny hole punched in it, so a thin stream of color recorded his journey. On another, his sweater unraveled step by step. This project and book began when Alys heard about the Tehuelche people of Patagonia, who gather seasonally to hunt the local flightless birds, nandus, by tracking them over hundreds of kilometers until the birds collapse from exhaustion. “I was fascinated by the absolute simplicity of the technique, and of course the use of walking as a weapon, as a hunting method, Alys says. As Alys sifted through the film he’d shot over three years documenting the hunt, he noticed that mirages became visible on the horizon of a dusty, endless highway and the final work became a two-minute 16mm film showing nothing more than a trip along a highway with an incessantly blurring, unreachable horizon.