According to Chapter 10, what was so mysterious about Sai Baba's sleeping arrangements?

Chapter 10 provides a fascinating description of Sai Baba's sleeping arrangements. He would sleep on a very narrow wooden plank, only about one span (or nine inches) wide and four cubits long. This plank was suspended from the rafters like a swing, tied at both ends with old rags. What made this truly mysterious, as the chapter highlights, was that His movements were completely imperceptible. No one ever saw when He climbed up onto the plank or when He descended from it. He would simply be seen sitting or sleeping there, with lamps burning at his head and feet, but the process of getting there remained an enigma to all.