O woman! in our hours of ease

Uncertain, coy, and hard to please,

And variable as the shade

By the light quivering aspen made;

When pain and anguish wring the brow,

A ministering angel thou!

Sir Walter Scott (1771-1832): Marmion. Canto vi. Stanza 30.

  Rom.  Lady, by yonder blessed moon I swear,

That tips with silver all these fruit-tree tops—

  Jul.  O, swear not by the moon, the inconstant moon,

That monthly changes in her circled orb,

Lest that thy love prove likewise variable.

William Shakespeare (1564-1616): Romeo and Juliet. Act ii. Sc. 2.