Manava Dharmashastra 2.63

2.63

uddhṛte dakṣine pāṇāv upavīty ucyate dvijaḥ
savye prācīnāvītī nivītī kaṇṭhasajjane //

A twice-born man is called upavitin when his right arm is raised (and the sacrificial string or the dress, passed under it, rests on the left shoulder); (when his) left (arm) is raised (and the string, or the dress, passed under it, rests on the right shoulder, he is called) prakinavitin; and nivitin when it hangs down (straight) from the neck.