The tradition holds Mañjushrīmītra to have first codified Atiyoga into these three indivisible sections, namely: Semde (mind class/cycle); Longde (space class/cycle); and Mengagde (direct/oral instruction class/cycle).
Traditionally, Mañjushrīmītra (Tib. jam dpal bshes gnyen) is said to have classified all the Dzogchen teachings transmitted by his teacher Prahevajra (Tib. Garab Dorje) into three series: Semde (Wylie: sems sde), Longde (Wylie: klong sde), and Menngagde.