A historical mead method summarized from Columella's Res rustica XII.41, combining grape must and honey and fermenting it for 31 days.
Historical recipe, not a modern tested mead formula. The source explicitly says the author summarized Columella's method and had not personally prepared it. Modern fermentation sanitation, vessel, airlock, and food-safety practices should be used rather than literally reproducing ancient plaster-sealing methods.