सर्पवद्रज्जुखण्डस्तु निशायां वेश्ममध्यगः ।एको हि चन्द्रो द्वौ व्योम्नि तिमिराहतचक्षुषः ॥
In plain words
Just as a piece of rope inside a house at night is mistaken for a snake, or the single moon in the sky appears as two to eyes clouded by a cataract.
Close to the Sanskrit
A piece of rope in the house at night [appears] like a snake; [and] indeed the one moon in the sky [appears as] two to one whose eyes are smitten by darkness.