According to Sri Vaishnavism, liberated souls who reach Vaikunta, the eternal inhabitants of Vaikunta, and Para Vasudeva, all have bodies made of Shuddha Sattva matter, which is achit that doesn't have rajas and tamas. This is unlike Prakriti, which is achit that has all 3 gunas.
So which scripture is this concept of Shuddha Sattva from?