  Suggested by Scullard's recent star-triangle relation for bond correlated
systems, we propose a general "cell/dual-cell" transformation, which allows in
principle an infinite variety of lattices with exact percolation thresholds to
be generated. We directly verify Scullard's new site percolation thresholds,
and derive the bond thresholds for his "martini" lattice (pc = 1/sqrt(2)) and
the "A" lattice (pc = 0.625457..., solution to p^5 - 4 p^4 + 3 p^3 + 2 p^2 - 1
= 0). We also present a precise Monte-Carlo test the site threshold for the "A"
lattice.
