Queen Mab

MERCUTIO
[...]
This is that very Mab
That plats the manes of horses in the night,
And bakes the elflocks in foul sluttish hairs,
Which once untangled, much misfortune bodes:
This is the hag, when maids lie on their backs,
That presses them and learns them first to bear,
Making them women of good carriage:
This is she--

ROMEO Peace, peace, Mercutio, peace!
Thou talk'st of nothing.

MERCUTIO True, I talk of dreams,
Which are the children of an idle brain,
Begot of nothing but vain fantasy,
Which is as thin of substance as the air
And more inconstant than the wind, who wooes
Even now the frozen bosom of the north,
And, being anger'd, puffs away from thence,
Turning his face to the dew-dropping south.

Romeo & Juliet. Act I Scene IV