Matsyapurana 144.21

144.21

teṣāṃ medhāvināṃ pūrvaṃ martye svāyambhuve 'ntare
utpasyantīha śāstrāṇāṃ dvāpare paripanthinaḥ //

When they became disappointed they sought means to get rid of their distress As a consequence they began to find faults with worldly things Out of this fault finding true knowledge arose Of the wise Munis in the Svayambhuva Manvantara, some turned out in the Dvâparayuga as the opponents of the Vedas Then Âyurveda (medicine), astronomy and the other limbs of the Vedas political economy, logic, metaphysics the ceremonies of the Kalpa Sûtras, the glosses, the Smṛitis, and various other Śâstras became filled with doubts No effort was crowned with success, unless the whole body, mind and deed were set to work—20-24