  The ground state properties of the pure perovskite compounds PrMnO$_3$ and
NdMnO$_3$ were investigated by magnetization, magnetic AC susceptibility and
specific heat measurements. A strongly anisotropic behavior has been detected
for temperatures below the antiferromagnetic phase transition $T_N$~100K. The
susceptibility and the weak spontaneous ferromagnetic moment appear to be
different in both compounds due to different anisotropic rare earth
contributions. The specific heat shows strong Schottky type contributions at
low temperatures, which for NdMnO$_3$ strongly depend on the magnetic field. A
spin reorientation phase transition (spin-flop type) induced by a magnetic
field along b axis was observed in NdMnO$_3$ at H~110kOe and T=5K. All results
can consistently be explained by anisotropic contributions of the rare earth
ions: In PrMnO$_3$ the electronic ground state is determined by a low lying
quasidoublet split by the crystal field ~19 K. In NdMnO$_3$ the Kramers doublet
is split by an exchange Nd-Mn field (~20K).
