Abba Binyamin says: If the eye was given permission to see, no creature would be able to withstand the demons.

Abaye said: They are more numerous than we and they stand over us like mounds of earth surrounding a pit.

Rav Huna said: Each and every one of us has a thousand to his left and ten thousand to his right.

One who seeks to know should place fine ashes around his bed, and in the morning appear like chickens’ footprints. One who seeks to see them should take the afterbirth of a firstborn female black cat, born to a firstborn female black cat, burn it in the fire, grind it and place it in his eyes, and he will see them. Place in an iron tube sealed with an iron seal [gushpanka] lest the demons steal it from him, and seal the opening so he will not be harmed. Rav Beivai bar Abaye performed this, saw, and was harmed. The Sages prayed for mercy on his and he was healed.

–Babylonian Talmud Berachot 6a