Charak Samhita
द्विविधमेव खलु सर्वं सच्चासच्च; तस्य चतुर्विधा परीक्षा- आप्तोपदेशः, प्रत्यक्षम्, अनुमानं, युक्तिश्चेति ॥१७॥
॥ Four-fold examination॥ All the worldly objects can be divided into two categories, truth (or existence) and false (or non-existence). There are four methods of examination- scriptures or texts (words of persons with superior intellect, or sages), direct perception (direct observance), inference and reasoning.
english translation
dvividhameva khalu sarvaM saccAsacca; tasya caturvidhA parIkSA- AptopadezaH, pratyakSam, anumAnaM, yuktizceti ॥17॥
hk transliteration by Sanscript