How did Sai Baba demonstrate the sanctity of his own feet to Das Ganu in Chapter 22?

Chapter 22 recounts a powerful story of how Sai Baba demonstrated the sanctity of His feet to His devotee, Das Ganu. When Das Ganu sought permission to go on a pilgrimage to bathe in the holy waters of Prayag, the confluence of the Ganga and Yamuna rivers, Baba instructed him differently. According to the text, Baba told him, 'Know this big toe of Mine to be Prayag; bathe right here.' When Das Ganu obediently placed his head on Baba's feet, the waters of both the Ganga and Yamuna miraculously manifested right from Baba's big toe, fulfilling the devotee's desire.