Can you elaborate on the concepts of Purusha, Avyakta, and Maya as presented in the philosophical discourse of Chapter 19?

Chapter 19 presents a hierarchy of subtlety in existence. It states that the Soul (Atma) is a Great Power. Subtler than the Soul is the Unmanifest (Avyakta), which is described as Space or Unmanifest Nature, also called Maya. This Maya is the force through which the changeless Soul appears to act in the world. However, the text clarifies that subtler than all of these is the Purusha, the Supreme Being. This Purusha is the ultimate goal where the senses and mind finally find rest. This state is identified as the Pure Brahman, the ultimate reality beyond the illusions created by Maya and the cycle of worldly existence.