Natyashastra
उद्वाह्य गात्रं पादं च सोपाने निक्षिपेन्नरः । तथावतरणं चैव गात्रमानम्य रेचयेत् ॥ ९८॥
A person should raise the body and foot, and place the foot on the stair; Likewise, descending should be done by gradually lowering the body and foot in a proper manner.
english translation
udvAhya gAtraM pAdaM ca sopAne nikSipennaraH । tathAvataraNaM caiva gAtramAnamya recayet ॥ 98॥
hk transliteration by Sanscript