Here is a SQL script to calculate MINX,MINY,MAXX,MAXY.
select "STATE_NAME" AS statename,
xmin(ST_EXTENT(ST_Envelope(wkb_geometry))) as MINX_26985,
ymin(ST_EXTENT(ST_Envelope(wkb_geometry))) as MINY_26985, xmax(ST_EXTENT(ST_Envelope(wkb_geometry))) as MAXX_26985,
ymax(ST_EXTENT(ST_Envelope(wkb_geometry))) as MAXY_26985,
xmin(ST_Transform(ST_GeomFromText(ASTEXT(ST_EXTENT(ST_Envelope(wkb_geometry))),26985),4326)) as XMIN_4326,
ymin(ST_Transform(ST_GeomFromText(ASTEXT(ST_EXTENT(ST_Envelope(wkb_geometry))),26985),4326)) as MINY_4326,
xmax(ST_Transform(ST_GeomFromText(ASTEXT(ST_EXTENT(ST_Envelope(wkb_geometry))),26985),4326)) as MAXX_4326,
ymax(ST_Transform(ST_GeomFromText(ASTEXT(ST_EXTENT(ST_Envelope(wkb_geometry))),26985),4326)) as MAXY_4326 from "states" group by "STATE_NAME"
Here are, how the results look like at PG-ADMIN GUI.
Last step is to verify, what we have done in the same environment.
I verified with quantum gis(Extension: PG Query for QGIS) for one of the bounding box "POLYGON((-197183.109375 -124668.3828125,-197183.109375 200596.6875,554324.75 200596.6875,554324.75 -124668.3828125,-197183.109375 -124668.3828125))" and here is how it looks like,
