The tired feeling in my legs, according to a note which I find I made upon the dream, had been a real sensation during the day-time. It probably went along with a tired mood and a doubting thought: 'How much farther will my legs carry me?' The end of the adventure in She is that the guide, instead of finding immortality for herself and the others, perishes in the mysterious subterranean fire. A fear of that kind was unmistakably active in the dream-thoughts.
(Freud, 1900 [SE 5], p. 454)