Natyashastra
व्यायामं कारयेत् श्रीमान् भित्तावाकालिके तथा । योग्यायां मातृका भित्तिस्तस्माद्भित्तिं समाश्रयेत् ॥ ९८॥
A noble person should perform exercises against a wall or in open space. The wall is considered the proper support for exercise, and hence one should resort to it.
english translation
vyAyAmaM kArayet zrImAn bhittAvAkAlike tathA । yogyAyAM mAtRkA bhittistasmAdbhittiM samAzrayet ॥ 98॥
hk transliteration by Sanscript