The main objective of this paper is to review the phenomenon of the Spanish seseo in a sample of documents from Nuevo Reino de Granada registered during the seventeenth and eighteenth centuries. The sources were two corpus of Neogranadian Spanish; namely, Documentos para la historia lingüística de Colombia (DHLC), and the corpus from the project of the Asociación de Lingüística y Filología de América Latina (ALFAL) titled Historia del español de América. The tool used to fulfil this work was AntConc. Through this, samples subject to review were filtered. The data account for the existence of seseo in the period when the texts were produced. Among other phenomena, alternations as <ce> ~ <ze> that are likely to be interpreted either as a distinction awareness between voiceless alveolar fricative /s/ and voiceless interdental fricative consonants /θ/, or as consciousness of an orthographic pattern, proving instability in phoneme-grapheme relation.