Special meetings of the Council may be called by the Clerk on the request of the Mayor, any three (3) members of the Council, or the City Administrator on at least eighteen (18) hours notice to each member of the Council, designating the time, place, and purpose of any such meeting. Any special meeting of the Council at which not less than four (4) members of the Council are present or have in writing waived the requirement that notice be given at least eighteen (18) hours prior to the time specified for the holding of such meeting and at which a quorum of the Council is present, shall be a legal meeting.