how much weight was patient 12952's first weight on the first hospital visit?
select chartevents.valuenum from chartevents where chartevents.icustay_id in ( select icustays.icustay_id from icustays where icustays.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 12952 and admissions.dischtime is not null order by admissions.admittime asc limit 1 ) ) and chartevents.itemid in ( select d_items.itemid from d_items where d_items.label = 'admit wt' and d_items.linksto = 'chartevents' ) order by chartevents.charttime asc limit 1