Rahasya Traya Saram (also spelled Rahasyatraya Sara) is a seminal work in the Śrī Vaishṇava tradition, composed by the great Acharya Vedanta Desika (1268–1369 CE). The title translates to "The Essence of the Three Secrets" or "The Quintessence of the Three Mysteries."
You can find digital versions and scholarly translations of this text on several authoritative platforms: Archive.org (Public Domain): English Translation by M.R. Rajagopala Ayyangar (1946) : A classic, detailed translation rahasya traya saram pdf
Arthanusasana Bhaga: Outlines the core doctrines of Visishtadvaita philosophy. Guide to Rahasya Traya Saram PDF 1
The work is organized into 32 chapters (Adhikaras) grouped into four major sections (Bhagams): Sarva Siddha Siddhanta : This section deals with
SampradhAya PrakriyA BhAgam: Chapters 30–32, detailing the traditions, duties of a guru, and the life of a disciple. Srimad Rahasyatrayasaram of Sri Vedanta Desika