  We study nuclear spin frequency shifts in a $^{3}$He-$^{129}$Xe
comagnetometer caused by spin polarization of $^{3}$He. We use stemless
cylindrical cells to systematically vary the cell geometry and separately
measure the cell shape-dependent and shape-independent frequency shifts. We
find that a certain aspect ratio for a cylindrical cell cancels the dipolar
effects of $^3$He magnetization in the regime of fast spin diffusion. Using
this control we observe a scalar $^{3}$He-$^{129}$Xe collisional frequency
shift characterized by an enhancement factor $\kappa_{\text{HeXe}} =
-0.011\pm0.001$ in excellent agreement with theoretical calculation.
