status ) ▁people ▁such ▁as ▁J ang ▁Ye ong - sil ▁were ▁allowed ▁to ▁work ▁for ▁the ▁government . ▁At ▁a ▁young ▁age , ▁J ang ▁displayed ▁talent ▁as ▁an ▁invent or ▁and ▁engineer , ▁creating ▁machines ▁to ▁facil itate ▁agricult ural ▁work . ▁These ▁included ▁super vis ing ▁the ▁building ▁of ▁aqu ed uct s ▁and ▁can als . ▁J ang ▁eventually ▁was ▁allowed ▁to ▁live ▁at ▁the ▁royal ▁palace , ▁where ▁he ▁led ▁a ▁group ▁of ▁scient ists ▁to ▁work ▁on ▁adv ancing ▁Korea ' s ▁science . ▁ ▁Some ▁of ▁his ▁invent ions ▁were ▁an ▁autom ated ▁( self - st rik ing ) ▁water ▁clock ▁( the ▁Jag ye ok ru ) ▁which ▁worked ▁by ▁activ ating ▁mot ions ▁of ▁wooden ▁figures ▁to ▁indicate ▁time ▁vis ually ▁( in vent ed ▁in ▁ 1 4 3 4 ▁by ▁J ang ), ▁a ▁subsequent ▁more ▁complicated ▁water - clock ▁with ▁additional ▁astronom ical ▁devices , ▁and ▁an ▁improved ▁model ▁of ▁the ▁previous ▁metal ▁mov able ▁printing ▁type ▁created ▁in ▁the ▁G ory e o ▁D ynast y . ▁The ▁new ▁model ▁was ▁of ▁even ▁higher ▁quality ▁and ▁was ▁twice ▁as ▁fast . ▁Other ▁invent ions ▁were ▁the ▁sight ▁glass , ▁and ▁the ▁u dom eter . ▁ ▁The ▁high point ▁of ▁Korean ▁astronom y ▁was ▁during ▁the ▁Jose on ▁period , ▁where ▁men ▁such ▁as ▁J ang ▁created ▁devices ▁such ▁as ▁cel est ial ▁glob es ▁which ▁indicated ▁the ▁positions ▁of ▁the ▁sun , ▁moon , ▁and ▁the ▁stars .