▁the ▁English ▁queen ▁Mary ▁T ud or ▁to ▁Philip ▁II ▁of ▁Spain . ▁ ▁At ▁the ▁Ott oman ▁court ▁In ▁ 1 5 5 4 ▁and ▁again ▁in ▁ 1 5 5 6 , ▁Ferdinand ▁named ▁him ▁amb assador ▁to ▁the ▁Ott oman ▁Empire ▁under ▁the ▁rule ▁of ▁S ule iman ▁the ▁Magn ific ent . ▁His ▁task ▁for ▁much ▁of ▁the ▁time ▁he ▁was ▁in ▁Constantin ople ▁was ▁the ▁neg ot iation ▁of ▁a ▁border ▁treat y ▁between ▁his ▁employ er ▁( the ▁future ▁Holy ▁Roman ▁Emperor ) ▁and ▁the ▁Sultan ▁over ▁the ▁disput ed ▁territory ▁of ▁Trans ylvan ia . ▁He ▁had ▁no ▁success ▁in ▁this ▁mission ▁while ▁R ust em ▁P asha ▁was ▁the ▁Sultan ' s ▁viz ier , ▁but ▁ultimately ▁reached ▁an ▁accord ▁with ▁his ▁successor ▁Sem iz ▁Ali ▁P asha . ▁ ▁During ▁his ▁stay ▁in ▁Constantin ople , ▁he ▁wrote ▁his ▁best ▁known ▁work , ▁the ▁Turkish ▁Let ters , ▁a ▁comp end ium ▁of ▁personal ▁correspond ence ▁to ▁his ▁friend , ▁and ▁fellow ▁Hung arian ▁diplom at , ▁Nicholas ▁Mich ault , ▁in ▁Fland ers ▁and ▁some ▁of ▁the ▁world ' s ▁first ▁travel ▁literature . ▁These ▁letters ▁describe ▁his ▁advent ures ▁in ▁Ott oman ▁politics ▁and ▁remain ▁one ▁of ▁the ▁principal ▁primary ▁sources ▁for ▁students ▁of ▁the ▁ 1 6 th - century ▁Ott oman ▁court . ▁He ▁also ▁wrote ▁in ▁enorm ous ▁detail ▁about ▁the ▁plant ▁and ▁animal ▁life ▁he ▁encountered ▁in ▁Turkey . ▁His ▁letters ▁also ▁contain ▁the ▁only ▁surv iving ▁word