Initially (around 1980) stochastic procedures were used, in which the
particle velocities were regularly reset to random values picked from
the appropriate Maxwell-Boltzmann distribution. [Andersen 1980,
Later, deterministic and even reversible equations of motion
were developed that nevertheless serve to roam phase space in a
more or less ``canonical'' manner. These are known as
Gaussian and Nose-Hoover dynamics, respectively.