In each census from 1850-1930, the census bureau issued written instructions to individuals hired to take the census. These instructions help explain the sometimes mysterious data recorded on the schedules.
U.S. Census Office. 12th Census, 1900...Instructions To Enumerators. Call# Govt I 13:7:7-653.
Enumerator Instructions: 1850-2000. Part of the Integrated Public Use Microdata Web site from the Minnesota Population Center at the University of Minnesota .