Constancy: The Star to Every Wand'ring Bark

Julius Caesar, 3.1.64-71:

CAESAR (after CASSIUS joins his plea to that of METELLUS and BRUTUS):

I could be well moved, if I were as you:
If I could pray to move, prayers would move me:
But I am constant as the northern star,
Of whose true-fix'd and resting quality
There is no fellow in the firmament.
The skies are painted with unnumber'd sparks,
They are all fire and every one doth shine,
But there's but one in all doth hold his place:

Sonnet 116, ll. 2-8:

... Love is not love
Which alters when it alteration finds,
Or bends with the remover to remove.
O no! it is an ever-fixed mark 
That looks on tempests and is never shaken;
It is the star to every wand'ring bark,
Whose worth's unknown, although his height be taken.