In ancient times the Japanese doctor or pharmacist was expected to concoct a special formula that would cure the patient. The pressure to find the correct mixture of ingredients was so great that many a doctor would hurl the measuring spoon into the air in despair.
Metaphorically, saiji o nageru means to give up out of frustration. Often the phrase is used as admonishment not to give up.
Kyooikusha naru mono wa, donna gakusei ni taishite mo saji o nagete wa naranai. Ningen wa dare de mo nanika no kakusareta sainoo ga aru mono da kara dearu.
Educators must not give up on any student, for every human being has some ability yet to be tapped.