Can you tell me about the practitioner of Yoga who visited Baba in Chapter 23?

Certainly. Chapter 23 recounts the story of a practitioner of Yoga (Yogabhyasi) who came for Sai Baba's darshan accompanied by Nanasaheb Chandorkar. This yogi was highly learned, having thoroughly studied the Yoga Shastras of Patanjali and others, yet he struggled to achieve Samadhi (intense meditation) for even a moment. Believing that 'Maharaj Sai is a King of Yogis,' he hoped that Baba's grace would remove his doubts and help him attain his goal. However, upon arriving at the Masjid for darshan, his expectation of a profound mystical encounter was met with the sight of Sai Baba simply eating bread (bhakar) with onions.