Do not speak in the bathroom. Do not walk into ruins
even if you need to pray undisturbed.
At night, carry a torch, or wait for the moonlight;
better still, walk on deserted paths only with friends.

Be sure to say the right words before you retire to bed.
These life-forms are more numerous than us —
be satisfied you haven't been given permission to see them
because your mind would not withstand the sight.

Ten thousand of them are by your right hand,
one thousand by your left, swarming all around you.
They cause the fatigue of knees and the pain of feet,
the overcrowding at lectures, the wearing-out of garments.

If, despite the danger, you still wish to see them,
take the placenta of a first-born female black cat
born from another first-born, burn it in the fire,
grind it down and place the ashes in your eyes.

These are only partial instructions. Don't get yourself into trouble
unless you have a group of sages praying for your safety;
learn from the example of Rav Beivai bar Abaye
who tried the procedure and came to harm.

References, in order of appearance: Babylonian Talmud, tractate Berachot
62a, 3b, 43b, 5a, 6a