1880 Home with Ballon Framing - Roof Soffit Question
Wire mesh for birds/squirrels (while permitting ventilation) louvers (usually small metal vent louver strips) to block birds and light (to an extent) if blocking light is important to you. If blocking light better than simply using louvers is desired you might need to construct a soffit externally which would typically have the vent louvers in the bottom. Some sort of internal baffle could also be arranged, if more convenient.
Unclear what your insulation and associated ventilation needs are, but typically &quot;cold roof&quot; setups require vents at the eaves and other vents at or near the peak (typically gable end and/or cupola vents on that era building, as built, anyway.)