  The inherent self-consistency properties of the six-point multi-ratio
equation allow it to be considered on a domain associated with a T-shaped
Coxeter-Dynkin diagram. This extends the KP lattice, which has A_N symmetry,
and incorporates also KdV-type dynamics on a sub-domain with D_N symmetry, and
Painleve dynamics on a sub-domain with affine-E8 symmetry. More generally, it
can be seen as a distinguished representation of Coble's Cremona group
associated with invariants of point sets in projective space.
