I felt a Cleaving in my Mind — Jigsaw Puzzle

I felt a Cleaving in my Mind－¹
As if my Brain had split－
I tried to match it－Seam by Seam－
But could not make it fit.

The thought behind, I strove to join ⁵
Unto the thought before－
But Sequence ravelled out of Sound
Like Balls－upon a Floor.

(F.867/J.937)

[1, 2] Cleaving, split:: a hint on puzzle with pieces of a cardboard.
[3, 4, 5] match, fit, join:: ways to solve the puzzle.
[6] thought before:: the original form of the puzzle before cut.
[7] out of Sound:: randomly.
[8] Balls, Floor:: pieces all alike spreading on the floor.