§ 140. Trusts for public parks, playgrounds, libraries and public buildings. It shall be lawful to grant and devise real estate, and to give and bequeath personal property to trustees and their successors in trust, for the purpose of creating, continuing and maintaining, according to the terms, conditions and provisions of such grant, gift, devise or bequest, one or more public parks, or public playgrounds, or a public library, or a public building, or for the purpose of aiding and instructing children, or for any one or more of such purposes, in any city, village or town of this state. The number of such trustees shall not be less than three nor more than nine.