FWP:
For background see S. R. Faruqi's choices. For more on Ghalib's unpublished verses, see the discussion in {4,8x}.
The claim that in order to teach a parrot to talk, the trainer speaks from behind a mirror, is one that Gyan Chand makes elsewhere as well; for more discussion, see {29,2}. Gyan Chand seems to take it that the poet speaks from behind the 'mirror' of his poetry, so that the amazement and astonishment of the 'parrot'-listener gazing into the mirror works to the poet's advantage. The poet can thus create the most astonishing effects of form and even content, yet in his discreet hiddenness he cannot be reproached for anything he says. Asi and Zamin agree that the mirror is a 'shelter' [aa;R] behind which the hidden poet can think without distraction and speak without fear.
But then on that reading, why does the poet sit behind the 'knee' of the mirror [zaanuu-e aa))iinah]? When it comes to 'knees', we might think of that ubiquitous South Asian style of sitting on the haunches called do-zaanuu bai;Thnaa (for discussion see {32,2}). But it's hard to imagine that the mirror somehow sits there on its 'haunches'.
Instead, we could invoke another quite possible reading of the i.zaafat , and could consider that the speaker sits behind 'the knee that is a mirror' or 'the knee that has the property of a mirror'. In his discussion of {213,1}, Nazm says, 'In the state of thought, to be 'head on knee' [sar bah zaanuu] has become habitual; for this reason, in the literature of the Persian-users [faarsii-vaale] the 'knee of thought' is among the affinities, and to call the knee a 'mirror' is a well-known thing'. If the speaker is seated, eyes lowered, deep in thought, then his face is aimed downward and at a forward angle, looking (unseeingly?) at his knee from above and 'behind' it. His regarding the 'knee-mirror' like this keeps him motionless and 'amazed'; on the nature of ;hairat , see {51,9x}. His heart itself 'seats' him in this position, so that he can best devote himself to the 'thought of poetry'.
But just as the commentators' reading can't make use of the 'knee of the mirror', my reading can't make any special use of saaz-e salaamat (as their 'shelter' reading can). Which of the various meanings of saaz (see the definition above) is to be foregrounded, and why? And in what sense is saaz to be characterized by, or productive of, 'well-being'? And where is the poetic 'proof' that poetry-composition is such a saaz-e salaamat ?
Thus neither reading is able to create a satisfactory amount of connection between the two lines. Perhaps some other, better reading eludes us. Or perhaps Ghalib himself decided that this was a verse that didn't really need to be in his published divan.
Asi:
The amazement that I feel in the thought of poetry, is for me the making/equipment of well-being. In this situation my heart, so to speak, hides me in the shelter of a mirror and sits me down safely, and I keep being saved from other cares of the world.
== Asi, p. 264