Natyashastra
वैशाखस्थानमेतद्धि स्कन्दश्चात्राधिदैवतम् । स्थानेनानेन कर्तव्यमश्वानां वाहनं बुधैः ॥ ६३॥
This is the Vaiśākha Sthāna, and its presiding deity is Skanda. This stance should be used by the wise for mounting horses.
english translation
vaizAkhasthAnametaddhi skandazcAtrAdhidaivatam । sthAnenAnena kartavyamazvAnAM vAhanaM budhaiH ॥ 63॥
hk transliteration by Sanscript