The Inverness Cape evolved into it's current form by the late 1800's. Instead of sleeves, it has wide arm holes cut-out under a cape. I think for this reason, the Inverness Cape has remained so popular for wear with the kilt — you don't have to unbutton the front to access your sporran! Just pull your arms back through the generous arm holes and get your flask out. (What other reason would you need to access your sporran in a rain storm? :-)
Dance piper Colin Gemmell, wearing an Inverness rain cape at the 2007 Tacoma Highland Games. copyright © 2007 by photographer James F. Perry. Used with permission under the Creative Commons Attribution - ShareAlike 3.0 license.