The council shall, by ordinance, fix the time for its regular meetings. Special meetings shall be called by the clerk of the council upon the written request of the mayor or any three councilmen [councilmembers]. At least twelve hours’ notice shall be given to the other members of the council, of the purpose, place and time of any such special meeting. Special meetings may also be held at any time without notice, provided all members of the council are present. No business shall be transacted at any such special meeting which is not stated in the notice calling the same, unless all members of the council attend the meeting or waive notice thereof. However, in case of an emergency, which is certified to be an emergency by a quorum of the council, a special meeting may be held to handle emergency matters.