Erroneous perception (pratyakṣābhāsam, 似現量) is a conceptual cognition (kalpanā-jñānam, 有分別智) in which an object (artha, 義) other than [what is being presently non-conceptually cognized seems to be perceived]. For instance, a cognition of a 'jar' or 'robe' that arises from conceptualization (vikalpa, 分別), since it is not the sva-lakṣaṇa 自相 of those [conceptually-created] objects (arthas 義) that is taken as a perceptual-object (viṣaya 境界), that perception is erroneous.

kalpanā-jñānam arthântare pratyakṣābhāsam yaj jñānaṃ ghaṭaḥ paṭa iti vā vikalpayataḥ samutpadyate tad artha-svalakṣaṇāviṣayatvāt pratyakṣābhāsam

有分別智。於義異轉。名似現量。謂諸有智了甁, 衣, 等, 分別而生。由彼於義 不以自相 爲境界故。名似現量。

A nonconceptual perception of a jar is a proper perception; to identify it as a 'jar' or 'such and such an item' introduces something beyond perception. The Sanskrit (but not the Chinese) signals this by the use of ' iti ' (yaj jñānaṃ ghaṭaḥ paṭa iti), which here indicates quotation marks, i.e., 'scare-quotes' to point out that it is the conceptualization of a jar, not the actual physical object being perceived, that is introducing the error. It is not that one does not see, feel, etc., a certain jar somewhere and sometime; rather it is the identification of that percept with a concept of 'jar' as if that concept inhabited the jar itself, or 'seeing' that particular jar as participating in a class of 'jar-ness,' etc., which is the problem.

Other types of erroneous perception, such as hallucinations, or seeing a 'double moon' (見第二月) as a result of an eye-illness (眼錯亂, cf. Ālambana-parīkṣā 觀所緣緣論 T 1624.31.888b19), are the result of erroneous superimpositions of conceptual content into perception, displacing an actual percept in oneʼs cognition with something remembered from a previous perception, or defective sense organs, etc. (Tib. mngon sum ltar snang) 〔因明入正理論 T 1630.32.12c6 〕