Special meetings of the board may be called at any time by order of a majority of the directors. Any member not joining in said order shall be given, by United States mail, at least a three days' notice of such meeting, unless the same is waived in writing, which notice shall also specify the business to be transacted and the board at such special meeting shall have no authority to transact any business other than that specified in the notice, unless the transaction of any other business is agreed to in writing by all the members of the board.