Measure for Measure
How we cite our quotes:
Behold, behold. where Madam Mitigation comes! I
have purchased as many diseases under her roof as come to--
To what, I pray?
To three thousand dolours a year.
Ay, and more.
A French crown more.
Thou art always figuring diseases in me; but thou
art full of error; I am sound. (1.2.9)
When Lucio talks about how much money he's spent at Mistress Overdone's brothel, he associates coins with venereal disease. A "French crown" is a French gold coin and also refers to a bald head, which is an unfortunate consequence of the "French disease" (syphilis).
This is pretty gross, but Lucio's logic also makes a lot of sense because coins are put into circulation in the same way that venereal diseases (like syphilis) are exchanged.