Jessie H. Bancroft's 1909 book Games for the Playground... describes it as follows.
Children form a ring clasping their hands around a much smaller "poison" circle drawn on the floor or ground.
The safety consists of finding a piece of dead wood, step on it.
Players tagged while caught off the wood become poisoned themselves and join the catchers.
[2] A simpler version, sometimes played by Scouts, is that whoever touches the "poison" drops out of the circle until only two players are left.