Cupid is a knavish lad, Thus to make poor females mad

And therefore is winged Cupid painted blind.

ROSALIND
A traveller! By my faith, you have great reason to be sad. I fear you have sold your own lands to see other men's; then to have seen much and to have nothing is to have rich eyes and poor hands. 

I essentially am not in madness, but mad in craft.

Thus conscience does make cowards of us all.

POLONIUS My lord, the queen would speak with you, and presently.
HAMLET Do you see yonder cloud that's almost in shape of a camel?
POLONIUS By th'mass, and 'tis like a camel indeed.
HAMLET Methinks it is like a weasel.
POLONIUS It is backed like a weasel.
HAMLET Or like a whale?
POLONIUS Very like a whale.
HAMLET Then I will come to my mother by and by. - They fool me to the top of my bent. - I will come by and by.