you need a hammer and an old wide edge wood chisel.
Find a starting place and just begin prying. You will find that once you start, they begin to fall off. Be sure to line your bath tub and sink and floor because when they fall off, they can ding the porcelin on these appliances.
To find a starting place, wallop a 4x4 tile in the center and begin chiseling out the pieces, then you have a place to move on