  When electrons flow as a viscous fluid in anisotropic metals, the reduced
symmetry leads to a viscosity tensor with additional, non-standard components.
Here we present a symmetry-based viscometry technique that can can directly
probe the entire viscosity tensor of an electron fluid, isotropic or otherwise.
By exploiting the symmetry of the fluid, our viscometry is exceptionally robust
to boundary complications and ballistic effects. In illustrating the technique,
we also propose an experiment for detecting rotational viscosity, universal to
anisotropic fluids, for the first time in a metal.
