create a box from point?

PGSQL 8.4.1  How can I create a box from point?

create table geo (id int, p point);
insert into geo values(1,'(143.032,-81.2315)');

SELECT ((p[0]-.5,p[1]-.5),(p[0]+.5,p[1]+.5)) AS boxx from geo;
                    boxx
-------------------------------------------
  ("(142.532,-81.7315)","(143.532,-80.7315)")

SELECT ((p[0]-.5,p[1]-.5),(p[0]+.5,p[1]+.5))::box AS boxx from geo;
ERROR:  cannot cast type record to box