From Hamlet
Hamlet: Do you see yonder cloud that’s almost in shape of a camel?
Polonius: By the 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.
'Methinks' is just a different way of writing 'IMO'. There similarity of cloud shapes to other objects is clearly subjective, not objective. Also, Polonius is coming across as a bit of a sycophant.