Zeeman perturbed nuclear quadrupole resonance was applied to evaluate weak magnetic fields
in the context of orbital currents in cuprate superconductors. The magnetic environment of the
barium atom in c-axis oriented powder samples of YBa2Cu4O8 was investigated in the pseudogap
phase at 90 K. No evidence for orbital currents was found: Any static and dynamic field must be
less than 0.07mT and 0.7mT respectively.