rajjusarpa nyāyaḥ (rope or snake)
A man in the dark mistakes the rope to be a snake or snake to be a rope.
In Vedic literature, such as Śrīmad-Bhāgavatam 6.9.37, this confusion is mentioned many times. The demigods are saying to Lord Viṣṇu:
sama-viṣama-matīnāṁ matam anusarasi
yathā rajju-khaṇḍaḥ sarpādi-dhiyām
A bewildered person considers a rope to be a snake, but not the intelligent one. In the same way, an intelligent person properly perceives Lord Viṣṇu as Supersoul, but less intelligent misconceives Him to be an ordinary person; one of us. Persons of this category prefer to put a snake on their lap, thinking it to be just rope. This is described in Bhāgavatam 10.6.8:
vibudhya tāṁ bālaka-mārikā-grahaṁ
carācarātmā sa nimīlitekṣaṇaḥ
anantam āropayad aṅkam antakaṁ
yathoragaṁ suptam abuddhi-rajju-dhīḥ
Pūtanā came to kill baby Kṛṣṇa, the all-pervading Supersoul, thinking him to be an ordinary baby. Instead, she was killed by Him, the small baby. She and other similarly scientifically political people are so foolish that they consider God to be a human, which is here likened to mistaking the sleeping snake to be a rope. For this group of people the illusion works both ways, unfavorably and dangerously. Both rope and snake are real. Mistaken perception is illusory. Krishna and Maya are real. To mismatch that is the work of illusion.