After 1920, since George Yeats found the sessions of Automatic Script increasingly draining, the Yeatses started the practice of ‘Sleeps', where George would enter a trance and speak, while W. B. Yeats noted what she said. These too decreased in frequency and ceased, apart from very occasional later instances, in 1924. George Mills Harper gives a clear summary in A Critical Edition of Yeats's A Vision (1925), xvii-xxiii.