This chart from Shaw-Perkins Radiators shows the various outputs in Btu/hr per square foot E.D.R. that you'll get at various steam pressures (including vacuum systems). Thanks to Patrick Linhardt for scanning and sharing this with us.
The Improved Webster Type "R" System of Steam Heating is a service bulletin from Warren Webster and Company (The Pioneers of Vacuum Steam Heating), established in 1888.
This manual was created by O-E Specialty Manufacturing Co. and outlines how to install the "O-E" Perfect System, which is a Vapor Vacuum heating system.
Here is the original Installation and Operating Instructions and Parts List for The H.B. Smith Company's Oil Fired Cast Iron Hot Water Boilers (No. OHB-13W). This is esti...