From Passenger Terminals and Trains, 1916 (reprint 1969). There is no plan and this book calls the station Northern Central Station. No floor plan for this station. Pages 96, 97.
Dimensions
Station building: Length 275 feet, Width 60 feet
Main waiting room: 65 feet wide, 95 feet long, 35 feet high
Train concourse is in two parts. One portion includes a covered lobby 330 feet long and 28 feet wide which extends along the track side of the station and connects with Charles Street bridge.
The other portion consists of an enclosed lobby, 50 feet wide, extending across the seven passenger tracks. This lobby opens onto the main waiting room. The tracks are 18 feet below the main floor of the station. There are eight stairways leading to train platforms. These platforms are 20 feet wide and from 600 to 1000 feet long.