Cite the scanned version of the original dicionary like this:
Bosworth, Joseph. "gang-setl." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth. Ed. Thomas Northcote Toller. Oxford: Clarendon Press, 1898. 361.
.Add: A stool (of a privy) :-- Þás úplendiscan wíf wyllað oft drincan and furþon etan fúllíce on gangsetlum . . . hit is bysmor þæt ǽnig man . . . þone múð ufan mid mettum áfylle, and on óðerne ende him gange þæt meox út fram, and drince þonne ǽgðer ge þæt ealu ge þone stenc, E. S. viii. 62, 13. v. next word.