What is the story of Das Ganu and the holy waters of Prayag as recounted in Chapter 22?

Chapter 22 recounts a significant event involving Das Ganu. When Das Ganu sought permission from Sai Baba to go on a pilgrimage to bathe in the holy waters of Prayag, Baba instructed him otherwise. Baba told Das Ganu, "Know this big toe of Mine to be Prayag; bathe right here." Trusting his Guru, Das Ganu placed his head upon Baba's feet. At that very moment, a miracle occurred. According to the account in Chapter 22, the holy waters of both the Ganga and the Yamuna rivers manifested right there from Baba's big toe, satisfying Das Ganu's desire for a holy bath and demonstrating the immense power contained within the Sadguru's feet.