(click to enlarge)
This is from 1824, and is from a book called Missionary Journal and Memoir of the Rev. Joseph Wolf: Missionary to the Jews (nice, huh?).
The search is difficult because---what would he be called? Throughout the 19th century one finds him called many things; Elijah Wilno, Rabbi Elia, Elijah Gaon and more. I'm sure there's something earlier--and I will find it!