Purandaropanishat - Sri Puranadara dasaru is said to have composed 425000 devaranamas. Of which only 1000 are available now. Sri Vyasarajaru kept the Devaranamas, SulAdi, and ugAbhOga along with svaramOla and did pooja for them and called the devaranamas by Purandaradasaru as “Purandaropanishat”, which is the gist of Bhagavatha and Upanishat.
From : https://www.facebook.com/116968631685816/photos/a.395939843788692/466708820045127/?type=1&theater