Here's the first OED entry for 'illume':
<pre> 
> illume
> 
> illume iliu.m, v. A poetical shortening of illumine: cf. relume,
> also used by Shaks. Perhaps influenced by Fr. allumer, rallumer (Of.
> alumer, ralumer), also OFr. enlumer, of which the stem -lumer came
> through *-lumner, from L. -luminare. = illumine: almost exclusively
> poetic.
> 
> 1. trans. To light up; to make shining or bright, to brighten.
> 
>    * 1602 Shaks. Ham. i. i. 37 When yond same Starre..Had made his
>      course t' illume that part of Heauen Where now it burnes.
> 
>    * 1788 Wolcott (P. Pindar) Peter's Pension Wks. 1812 II. 17
>      Train-oil instead of Wax was bid t'illume The goodly company
>      and Dancing-room.
> 
>    * 1791 Cowper Odyss. xix. 42 Pallas from a golden lamp illumed
>      The dusky way before them.
> 
>    * 1821 Shelley Hellas 69 A second sun array'd in flame, To burn,
>      to kindle, to illume.
> 
>    * 1875 Bedford Sailor's Pocket Bk. v. (ed. 2) 131 It illumes to a
>      greater extent the atmosphere.
> 
> 2. transf. and fig. To `light up' (the face), as a smile; to
> enlighten or illuminate (the mind or understanding).
> 
>    * A. 1764 Lloyd tr. Voltaire's Henriade Poet. Wks. 1774 II. 222
>      Descend, and with thy strong and purest light My verse illume!
> 
>    * 1795 Southey Vis. Maid Orleans iii. 146 Loftier thoughts illume
>      The enlighten'd glance.
> 
>    * 1804 J. Grahame Sabbath 311 A smile illumes The face of some.
> 
>    * 1862 Neale Hymns East. Ch. (1866) 57 Till through fast-closed
>      doors Thou camest Thy Disciples to illume.
> 
> 3. To set alight, kindle. Also, fig. Obs. rare.
> 
>    * 1728 Pope Dunc. iii. 260 Yon suns, he rears at pleasure higher,
>      Illumes their light, and sets their flames on fire.
> 
>    * 1744 Akenside Pleas. Imag. i. 363 She by this Illumes the
>      headstrong impulse of desire.
> 
> Hence
> 
> illumed
> 
> illumed iliu.md, ppl. a. Also
> 
> illumer
> 
> i'llumer, one who or that which illumes.
> 
>    * 1836 I. Taylor Phys. The. Another Life (1857) 179 A wide
>      illumed landscape.
> 
>    * 1854 Keightley Mythol. Anc. Greece (ed. 3) 384 Castor being the
>      Illumer.
</pre>
And here's the second, in which Emily Dickinson's use is quoted:
<pre>
> OED Entry Search
> 
> --------------------------------------------------------------------
> 
> illume
> 
> i'llume, sb. poet. rare. f. prec. vb. Illumination.
> 
>    * 1838 J. Struthers Poetic Tales 37 The lightnings flashed their
>      dread illume.
> 
>    * C. 1882 E. Dickinson Poems (1955) III. 1069 Better an ignis
>      fatuus Than no illume at all.
</pre>