Can you tell me about the Yogi who visited Sai Baba hoping to learn how to achieve Samadhi?

Certainly. Chapter 23 recounts the story of a practitioner of Yoga (Yogabhyasi) who came to Shirdi with Nanasaheb Chandorkar. This man had thoroughly studied the Yoga Shastras of Patanjali but was frustrated because he could not achieve Samadhi, even for a moment. He believed that Sai Baba, being a 'King of Yogis,' could grant him the grace to remove his doubts and attain this state of intense meditation. With this hope in his heart, he went for Baba's darshan. However, upon arriving at the Masjid, he was taken aback to see Baba engaged in the very ordinary act of eating bread (bhakar) with onions, which challenged his expectations of what a great yogi should be doing.