You said writing a Sadguru's biography is the best service. Does the book give any examples of saints who actually did this for their own Guru?

The preface, as presented in Chapter 0, describes writing the biography of one's own Sadguru as the 'best and most certain service' for attaining salvation, but it does not give any historical examples of specific saints who have performed this act. Instead, it presents this as an ideal principle and a recommended path for devotees. The author emphasizes that this form of service, when done with a pure heart and selfless love, is a profound practice of body and speech that can be performed without interfering with one's family or worldly responsibilities, and it encourages others to do the same.