To protect Mina from a possible vampire attack as they travel to Dracula's castle, Van Helsing draws a ring around where Mina sits by the campfire and sprinkles broken communion wafers along the circle. When Dracula's three "wives" or whatever they are visit, they are unable to pass the "Holy circle" to get at Mina. This entire scene is really cool the way Van Helsing thinks he might be imagining the three vampires at first as they seem to materialize out of the the wind and swirling snow. Then they are finally solid and he knows they're real and is relieved and thankful that the holy circle's power is strong enough to keep Mina and himself safe from their evil intentions, whatever they may be.
He holds out a bit of the wafer in front of him to step out of the circle to tend the fire. The vampires stay at bay outside the circle until dawn is near when they disappear into the wind again. He describes them as voluptuous, with bright eyes and white teeth. Isn't it odd that the female vampires become beautiful after death while Dracula was ugly with his long pointy teeth and bony body? However, their looks mean nothing to the poor horses who become so terrified by the vampires' presence that they die.
I've heard of people camping out in the winter, but I don't know how it's done. I kept thinking how cold Mina and Van Helsing must have been. They brought firewood and lots of furs with them for warmth, but there's no amount of furs and campfires that would keep me warm enough to camp out in the wind and snow!