Is "Mandation" a valid word?

The OED has a reference to it, though they clearly state that it is rare. But far from being a neologism the OED example is from1867.

Sc. Obs. rare.

Etymology: f. mandate v.: see ‑ation.

The action of committing a speech, etc., to memory.

1867 J. Macfarlane Mem. T. Archer i. 15 — Some of the most acceptable ministers of the Gospel have been known to regard ‘mandation’ as a process of slow murder.