http://swissbaync5d7ykaz7dh7v4qjrb4gmen5aj3bogxrcgbb43ij34bjuyd.onion/pdf/Books/Survival/Survival/measur.html
TIME AND DURATION: Their evaluation comes from a wide range of knowledge and habits where enters;
the habit to evaluate the hour by the sun, moon or star. The habit which becomes instinctive to know the darkening or increasing shadow
of the scenery, length and rhythm of step, the memory of the effort to do the
task, of the distance travelled, weather conditions, sense of rhythm to count
the seconds, you can count out loud, 331, 332, 333 ...