The terms Pramana viparyaya vikalpa nidra smrtayah describe the five mental modifications explained in the yogic texts. These represent the different ways the mind perceives and processes reality. Pramana refers to correct knowledge, while viparyaya means false understanding or illusion. Vikalpa is imagination without a real basis, nidra represents the mental state during deep sleep, ... https://www.yogkulam.org/blog/yoga-sutra-1-6-pramana-viparyaya-vikalpa-nidra-smrtayah