Chaucer, House of Fame
For when thy labour doon al ys,
And hast mad alle thy rekenynges,
In stede of reste and newe thynges,
Thou goost hom to thy hous anoon;
And, also domb as any stoon,
Thou sittest at another book
Tyl fully daswed ys thy look,
And lyvest thus as an heremyte,
Although thyn abstynence ys lyte.
In John Edmonds' modern English rendering:
When your labour is done, and you have made all your reckoning, instead of rest and new things you go home immediately to your house and also dumb as a stone you sit at another book until your looks are dazed, and live thus like a hermit, although your abstinence is small.
I would not translate "also domb as any stoon" as "also dumb as a stone." Rather I would translate it "as dumb as a stone." See the electronic Middle English Dictionary
, s.v. also (adv.) Also alswo, alz(u)o; alswa, alsway, alsqua, alsa; elswa; alse, als, as:
3a: In adverbial expressions: (a) introducing, connecting, or correlating prepositional phrases: also; and (..) also, and also; as..and, as..also; nought onli..but also; (b) correlated with a following as, so phrase or clause: as faste as, as fast as; etc.; (c) followed by a time clause or a clause of result: so.
Here, in my opinion, we have an example of (b). The Dictionary gives a comparable example, c1460 Oseney Reg.
118/11: Al so ofte as hit happeneth.