  We present results from light scattering experiments on three insulating
antiferromagnetic cuprates, YBa$_2$Cu$_3$O$_{6.05}$,
Bi$_2$Sr$_2$YCu$_2$O$_{8+\delta}$, and La$_2$CuO$_4$ as a function of
polarization and excitation energy {using samples of the latest generation.
From the raw data we derive symmetry-resolved spectra.} The spectral shape in
$B_{1g}$ symmetry is found to be nearly universal and independent of the
excitation energy. The spectra agree quantitatively with predictions by field
theory [\onlinecite{Weidinger:2015}] facilitating the precise extraction of the
Heisenberg coupling $J$. {In addition, the asymmetric line shape on the
high-energy side is found to be related to amplitude fluctuations of the
magnetization. In La$_2$CuO$_4$ alone minor contributions from resonance
effects may be identified.} The spectra in the other symmetries are not
universal. The variations may be traced back to weak resonance effects and
extrinsic contributions. For all three compounds we find support for the
existence of chiral excitations appearing as a continuum in $A_{2g}$ symmetry
having an onset slightly below $3J$. In La$_2$CuO$_4$ an additional isolated
excitation appears on top of the $A_{2g}$ continuum.
