秤砣虽小压千斤

although small, a steelyard weight may tip a hundred pounds (idiom) / apparently insignificant details can have a large impact / for want of a nail the battle was lost

variant of 稱|称[cheng1], to weigh

steelyard / Roman balance / CL:臺|台[tai2]

steelyard weight / standard weight

steelyard weight / stone roller / to polish jade with an emery wheel

although / even though

small / tiny / few / young

to press / to push down / to keep under (control) / pressure

see 壓根兒|压根儿[ya4 gen1 r5]

thousand

see 鞦韆|秋千[qiu1 qian1]

catty / (PRC) weight equal to 500 g / (Tw) weight equal to 600 g / (HK, Malaysia, Singapore) slightly over 604 g