Special meetings of the Council may be called as provided by its rules, regulations or bylaws, or by resolution or ordinance of the Council. In the absence of any such provision, special meetings may be called by a vote of Council taken at any regular or special meeting thereof or may be called by the Mayor, President of Council, President Pro Tem of Council, or any three members of the Council. The Clerk of Council, or in his absence, incapacity or refusal to act, the Mayor, shall cause notice in writing of each special meeting to be served personally or to be left at the usual place or residence of each member of the Council and the Mayor not less than twelve hours preceding the time for such special meeting. A copy of such notice shall be posted in the Council chamber at least twelve hours prior to such special meeting but failure to so post or to maintain posting for twelve hours shall not affect the validity of any meeting or any action taken at such meeting. In the event that a special meeting is called by a vote of Council taken at a regular or special meeting from which any member of Council or the Mayor is absent, written notice of such special meeting shall be given each absentee in the manner hereinbefore described. Service of notice of any special meeting shall be deemed conclusively to have been waived by any member of Council or the Mayor who shall be present at such special meeting.