What does Chapter 10 say is the easiest and most fruitful spiritual practice (Sadhana) for a person to undertake?

According to the beginning of Chapter 10, the best and simplest of all spiritual practices, or Sadhanas, is to always remember the Guru with a heart full of love. The text proclaims that this practice costs nothing, not even a single penny, yet yields great fruit with little effort. By the "mere remembrance" of the Guru, who is described as being eternally situated in the form of Brahman, the difficult "knot of birth and death is untied." This suggests that constant, loving remembrance is a direct path to liberation, superior to other complex methods, and should be practiced every moment while one's senses are still intact.