Act 4, Scene 1

Wales: near the cave of Belarius.

[Enter CLOTEN]
Cloten
2168 I am near to the place where they should meet, if
2169 Pisanio have mapped it truly. How fit his garments
2170 serve me! Why should his mistress, who was made by
2171 him that made the tailor, not be fit too? the
2172 rather—saving reverence of the word—for 'tis said
2173 a woman's fitness comes by fits. Therein I must
2174 play the workman. I dare speak it to myself—for it
2175 is not vain-glory for a man and his glass to confer
2176 in his own chamber—I mean, the lines of my body are
2177 as well drawn as his; no less young, more strong,
2178 not beneath him in fortunes, beyond him in the
2179 advantage of the time, above him in birth, alike
2180 conversant in general services, and more remarkable
2181 in single oppositions: yet this imperceiverant
2182 thing loves him in my despite. What mortality is!
2183 Posthumus, thy head, which now is growing upon thy
2184 shoulders, shall within this hour be off; thy
2185 mistress enforced; thy garments cut to pieces before
2186 thy face: and all this done, spurn her home to her
2187 father; who may haply be a little angry for my so
2188 rough usage; but my mother, having power of his
2189 testiness, shall turn all into my commendations. My
2190 horse is tied up safe: out, sword, and to a sore
2191 purpose! Fortune, put them into my hand! This is
2192 the very description of their meeting-place; and
2193 the fellow dares not deceive me.
[Exit]

Notes

TLN 2175archaic vocab
“vain-glory for a man and his glass to confer”
'Glass' here means mirror, not a drinking vessel. 'Confer' means to consult or hold conversation with. Cloten argues it is no boastfulness ('vain-glory') for a man to admire himself in his own mirror in the privacy of his own room — a self-serving justification for his vanity.
TLN 2181archaic vocab
“yet this imperceiverant thing loves him in my despite”
'Imperceiverant' means unable to perceive or understand — perceptually deficient. Cloten calls Imogen an 'imperceiverant thing' because she fails to see what he takes to be his obvious superiority to Posthumus in youth, strength, wealth, birth, military service, and single combat. The word appears nowhere else in Shakespeare and may be his own coinage. 'In my despite' means in defiance of me, or to spite me.
TLN 2182syntax grammar
“What mortality is!”
'Mortality' here does not mean death but humankind — the condition of being mortal, i.e. mere human beings. Cloten is exclaiming at the incomprehensibility of people: 'What a thing humanity is!' (that a woman would love an inferior man). A student reading this as a comment on death will misread the sentence entirely.