This paper examines self-inscription, a mode of census enumeration that emerged during the nineteenth century. Starting in the 1840s, a number of European states introduced self-inscription as an auxiliary means to facilitate the work of enumerators. However, a decisive shift occurred when Prussian census statisticians implemented self-inscription via individual "Zählkarten"-or "counting cards"-in 1871. The paper argues that scientific ideals of accuracy and precision prevalent in the sciences at the time motivated Prussian census officials to initiate self-inscription as an at-home scenario unmediated by enumerators, in which the census form alone was to yield truthful information from the respondents. By illuminating the bureaucratic means for implementing scientific ideals and practices in gathering personal census data, the paper offers an in-depth analysis of the media, technologies, and manpower that census takers deployed to reveal the epistemic-as well as social and political-impact of being "true to form."