Can you tell me about the mysterious wooden plank Sai Baba used for sleeping, as described in the text?

Chapter 10 provides a fascinating description of the wooden plank Sai Baba used for sleeping. This plank was remarkably narrow, measuring only one span (about 9 inches) wide and four cubits long. According to the text, it was suspended from the rafters like a swing, tied at both ends with old rags. Baba would sleep on this precarious plank with lamps burning at his head and feet. A key point of mystery highlighted in Chapter 10 is that his movements were imperceptible; no one ever knew when he climbed up or descended from it. The chapter suggests this was possible due to the Great Siddhis (powers) residing within him.