The interpretation of the imaginary unit as the ratio of two perpendicular vectors was proposed by Hermann Grassmann in the foreword to his Ausdehnungslehre of 1844; later William Clifford realized that this ratio could be interpreted as a bivector. Hestenes, David (1996). "Grassmann's Vision"(PDF). In Schubring, G. (ed.). Hermann Günther Graßmann (1809–1877). Springer. doi:10.1007/978-94-015-8753-2_20.
The interpretation of the imaginary unit as the ratio of two perpendicular vectors was proposed by Hermann Grassmann in the foreword to his Ausdehnungslehre of 1844; later William Clifford realized that this ratio could be interpreted as a bivector. Hestenes, David (1996). "Grassmann's Vision"(PDF). In Schubring, G. (ed.). Hermann Günther Graßmann (1809–1877). Springer. doi:10.1007/978-94-015-8753-2_20.