\[ \begin{aligned} \frac{dx}{dt} &= \sigma (y - x) \\ \frac{dy}{dt} &= x (\rho - z) - y \\ \frac{dz}{dt} &= xy - \beta z \end{aligned} \]
Paper: Lorenz, Edward N. "Deterministic nonperiodic flow." Journal of Atmospheric Sciences 20.2 (1963): 130-141.