Mass. Gen. Laws ch. 160 § 174
Every railroad car, except private cars, sleeping cars, dining cars, parlor cars, and the smoking, buffet and observation cars used in connection with the same, while in use for the transportation of passengers, upon a train running thirty miles or more, shall be provided with a sufficient quantity of pure drinking water in such place in the car as will be convenient for the passengers, and with individual drinking cups accessible to the passengers. Said cups shall be in a proper receptacle near the water tank, and said receptacle shall be so placed as to be easily seen and shall be plainly marked as follows:
such words to occupy a space not less than two inches wide by three inches long, and to be in clear black letters on a white background. No charge shall be made for the water or for the drinking cups. The water and cups supplied shall be subject to the supervision and approval of the department of public health, which shall enforce this and the following section.
Mass. Gen. Laws ch. 160, § 174