While writing about Gradus as a "transcendental tramp" I muddled a few words. Please note that its sentence inserted between bars should have been set down as

" - in spite of all his efforts and despite the transcendental power of literature and the fictional world - "

There's a line in CK's commentaries to line 596 that deals with another aspect of "Gradus," when CK considers Gradus' movements:

" What was Gradus doing that day? Nothing. Combinational fate rests on its laurels. "

The word "combinational" is not strange to the reader, but it's not related to "fate," or to "Gradus," but to John Shade.

1.

Knowing Shade’s combinational turn of mind and subtle sense of harmonic balance, I cannot imagine that he intended to deform the faces of his crystal by meddling with its predictable growth.( CK fwd)

2.

lines 971-977:

I feel I understand

                                                  Existence, or at least a minute part

                                                  Of my existence, only through my art,

                                                  In terms of combinational delight;

                                                  And if my private universe scans right,

                                                  So does the verse of galaxies divine

                                      Which I suspect is an iambic line.
                                                                                        ( J.S:PF)

3. "...our poet’s special brand of combinational magic "               ( lines 727-728)

So, I decided to follow C.K's steps to investigate what John Shade was doing that day, once the assassin's steps had been synchronized with his writing:  

While John Shade was composing Canto Three his poetic output didn't seem to be in any way different from his work on the other Cantos, those in which Gradus was actively setting out to meet him.

Why did CK make Gradus stop during fours days while JS kept moving his pen?

Line 596: Points at the puddle in his basement room
[  ] Shade composed these lines on Tuesday, July 14th. What was Gradus doing that day? Nothing. Combinational fate rests on its laurels. We saw him last on the late afternoon of July 10th when he returned from Lex to his hotel in Geneva, and there we left him.
// For the next four days Gradus remained fretting in Geneva. The amusing paradox with these men of action is that they constantly have to endure long stretches of otiosity that they are unable to fill with anything, lacking as they do the resources of an adventurous mind.

(from the fwd) "We possess in result a complete calendar of his work. Canto One was begun in the small hours of July 2 and completed on July 4. He started the next canto on his birthday and finished it on July 11. Another week was devoted to Canto Three. Canto Four was begun on July 19, and as already noted, the last third of its text (lines 949-999) is supplied by a Corrected Draft."

Knowing Nabokov's "combinational turn of mind" the immobility of Gradus must have been projectedonto J.Shade's verses. Has anyone already identified them?