The Collaborative International Dictionary of English v.0.48:
Middest \Mid"dest\, a.; superl. of Mid. [See Midst.] Situated most nearly in the middle; middlemost; midmost. [Obs.] " 'Mongst the middest crowd." --Spenser. [1913 Webster]The Collaborative International Dictionary of English v.0.48:
Middest \Mid"dest\, n. Midst; middle. [Obs.] --Fuller. [1913 Webster]