This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
A way to prevent any possible mistake of taking bottles containing poisons is to mark them as shown in the sketch. This method provides a way • to designate a poison bottle in the dark. The marker is made of a circle of heavy cardboard with a hole in the center so as to fit tightly over the neck of the bottle. No matter how dark it may be or how much of a hurry a person may be in, one cannot fail to note the character of the contents of the bottle as soon as the hand touches the cardboard marker. - Contributed by Katharine D. Morse, Syracuse, N. Y.