I dunno about boiling it, but the old timers around here used to collect pine tar by heating pine wood indirectly. They would find a big flat rock with just a bit of tilt to it, then chisel a small groove from the center to the edge. They would split a bunch of fat pine wood up kindling-sized and pack it in a big huge iron cauldron pot until they couldn't drive any more pieces of wood into the pot with a mallet. They would then turn the pot'o'pine upside down on the rock, seal the crack between the rock and the pot with clay except for the chiseled groove, which they would put a piece of tin or something over. Then they would build a big fire around the pot and as the wood heated, the tar ran out the groove into a waiting bucket.
