Long -long back in 1960-s after I  became a doctor  and  learned through Boyd's  Pathology Book that our body can accumulate from 500 m  to 1000 ml of fluid (water in  our system without giving  ant symptom  or sign clinically nor even a sign of  fluid accumulation in  costo-phrenic angle  to prove fluid in Pleural -space by X-ray of chest ( may not very  very accurate in my statement after about half a century i.e  today.
 But the interesting parallel I venture to draw is that : also  long after, I  studied a book  named Charak Sanghita  of AYURVEDA, i.e the knowledge  about LIFE and Health of INDIAN  VEDIC  period  (older than Even GREEK  CIVILISATION,)  where it was advised  for women who became pregnant , to wear a ring around the little toe the  foot (?left). And if the  lady  reported any feeling of tightening around, it was a sure way to know that water was getting accumulated in the body , That  was the first symptom & sign of  oedema or body-fluid Excess, when ,as proved in Modern Medicine, the Excess- accumulation of fluid was even  less than 500 ml in the  body.

What ?-- if in Modern days of Hypertension, , Circulatory diseases  or Kidney conditions, -if all men and women are advised to wear a ring around one of the little  toes!
Well this  is only the aftermath of my stray thought and is - no SCIENTIFIC  SERMON.