Special meetings shall be called by the City Clerk on written request of the Mayor, the City Manager or any three (3) Councilmembers. At least six (6) hours written notice shall be given to each Councilmember. Such notice shall contain a statement of the purpose of such meeting, such notice shall be delivered to each Councilmember personally. If this is not possible, then it shall be delivered to some responsible person at his or her residence. If this is not possible, then it must be left at his or her residence in some conspicuous place. Any special meeting shall be a legal meeting for all purposes without such notice, provided that all Councilmembers are present thereat or have waived notice thereof in writing, as to the purpose of said meeting not included in the notice thereof.