  We determine the optimal horoball packing densities for the Koszul-type
Coxeter simplex tilings in $\mathbb{H}^3$. We give a family of horoball
packings parameterized by the Busemann function and symmetry group that achieve
the simplicial packing density upper bound $d_3(\infty) = \left( 2 \sqrt{3}
\Lambda\left( \frac{\pi }{3} \right) \right)^{-1} \approx 0.853276$ where
$\Lambda$ is the Lobachevsky function.
