How did Sai Baba prove his omniscience to the skeptical Boss Dharamsee during his visit?

Sai Baba demonstrated his omniscience to Boss Dharamsee in a multi-layered event described in Chapter 35. First, as Dharamsee silently harbored a dislike for the seeded grapes being offered, Baba was fully aware of his inner turmoil and thoughts, including his doubt, 'If he is a saint, how does he not know I do not like these grapes?'. In response to this unexpressed thought, Baba gave him even more of the disliked grapes, showing he knew Dharamsee's mind. The ultimate proof came when Baba commanded him to eat, and the grapes miraculously turned out to be seedless. This confirmed to Dharamsee that Sai not only knew his innermost thoughts and preferences but also possessed the power to alter physical reality to address them, leading Dharamsee to exclaim, 'What a strange power! What is impossible for these saints?'