This paper presents a procedure for the determination of the dimensionality of the state space of a memristive device. The state space dimensionality of a device corresponds to the minimum number of time delayed values/derivatives of the voltage and current required to represent the device dynamics for a specified set of inputs. The algorithm is based on the observed time domain voltage-current (i.e. input-output) data which is obtained by measurement. The determination of the state space dimensionality is important to achieve a single-valued input-output multivariate mapping between the device outputs as a function of the embedding variables. In this paper, this will be accomplished using an embedding technique, based on the false nearest neighbor principle.