At the election the ballot shall contain the words "for the bonds" and "against the bonds" and to the right of and opposite each thereof shall be placed a square approximately the size of the squares placed opposite the names of candidates on ballots. The voter shall indicate his vote "for the bonds" or "against the bonds" by inserting a mark as defined in section 16-400 in the square opposite such words. No other question, word or figure need be printed on any ballot. The ballot shall not be of any particular size, and sample ballots may or may not be printed, posted or distributed. A number of ballots exceeding by not less than two per cent the number of registered voters whose names appear on the precinct register prepared for the precinct, town or city shall be printed for and furnished to each polling place.