We explicitly construct a particular real form of the Lie algebra ${𝔢}_7$ in terms of symplectic matrices over the octonions, thus justifying the identifications ${𝔢}_7\cong \mathrm{𝔰𝔭}(6,𝕆)$ and, at the group level, $E_7\cong \text{Sp}(6,𝕆)$. Along the way, we provide a geometric description of the minimal representation of ${𝔢}_7$ in terms of rank 3 objects called cubies.