Anusandhāna-rahasyam — The Dvaya to Be Continually Remembered
In the traditional classification of Rahasya-trayam, the Tirumantram is called mantra-rahasyam, the Dvaya Mahāmantram is called anusandhāna-rahasyam, and the Gītā Carama Śloka is called vidhi-rahasyam. Anusandhāna-rahasyam is therefore principally a designation of Dvayam, not the established title of a separate text that teaches three independent meditation techniques for all three rahasyas.
Anusandhānam means keeping the revealed meaning present in the mind through repeated remembrance and contemplation. Dvayam is especially suited for this because its first sentence expresses surrender at the feet of the Divine Couple as upāya, while its second sentence expresses eternal kainkaryam for Their pleasure as upeya.
In the Piḷḷai Lokācārya–Maṇavāḷa Māmunigaḷ tradition, Dvaya-anusandhānam is central to the prapanna's life. It is received with its meaning from the Āchārya and remembered not as a self-powered technique that earns liberation, but as the verbal and contemplative expression of dependence, gratitude, and the desired kainkaryam.
The meanings of Tirumantram and Carama Śloka are also repeatedly contemplated, but the technical name anusandhāna-rahasyam should not be broadened into an otherwise unattested standalone grantha covering all three.