What specific inspiration for writing the Shri Sai Satcharitra is mentioned in Chapter 40?

Chapter 40 reveals that the inspiration to write the book stemmed from the author witnessing Sai's profound and symbolic actions. The text specifically mentions the image of Sai, a saint, setting up a grinding stone and grinding grain. This act filled the author's mind with wonder and sparked a 'strong desire' to describe all such deeds. The motivation was a belief that chronicling these divine leelas would serve to destroy impurities and sins. The chapter further validates this by noting that God (Hari) is even more pleased when someone sings the praises of His devotees than when they praise God Himself.