The Mayor, President of Council, or any three members of Council may call special Council meetings upon at least 24 hours notice to the Mayor, President of Council and each Council member. Special Council meetings may also be called upon a vote of at least six Council members at any regular or special meeting thereof. The Clerk of Council, or in his or her absence, incapacity or refusal to act, the Mayor, shall cause notice of each special meeting to be served personally upon or to be left at the usual place of residence of each Council member, the President of Council and the Mayor. The notice shall state the nature of the matters to be considered at the special meeting. In the event that a special meeting is called by a Council vote taken at a regular or special meeting from which any Council member, the President of Council, or the Mayor is absent, written notice of such special meeting shall be given each absentee in the manner set forth above. Service of notice of any special meeting shall be deemed conclusively to have been waived by any Council member, the Mayor, or the President of Council who shall be present at such special meeting. The general public shall be notified of all special Council meetings and all such meetings shall be open to the public as provided in Section 3.12 of this Charter.