I found this old review from 1998 in New York Times of an exhibition of Steiner’s blackboard drawings.
Steiner wasn’t a professional artist; he dabbled in painting, to insipid effect. But he was a tireless lecturer and drew diagrams in colored chalk on slate blackboards as he talked. In 1919, one of his followers, Emma Stolle, hit on the idea of preserving the drawings by covering the slate with sheets of black paper before lectures began. She then dated the sheets and stored them away. […]
Some of the sparest images are the most evocative. The drawing titled ”Devoted Attention to the Least Thing” consists of nothing more than a tidy lineup of two circles, a cube, an upright pole and a mantra-like inscription (”In me is God, I am in God”).
The drawing mentioned is this one:
It’s from a lecture on curative pedagogy which Steiner held on July 5, 1924 (see GA 317). The accompanying words:
The mood of meditation should not be: I will inwardly lie down in a warm nest, which must become warmer and warmer for me. Rather, our mood must be that we are about to dip into reality, to grasp something real. Devoted attention to little things, indeed to the least thing, is what it comes down to.
In me is God
I am in God
The review continues:
Occult stuff-and-nonsense? Mondrian, Kandinsky and a host of other early modernist artists apparently didn’t think so. Nor did a more recent figure like Joseph Beuys, who produced his own blackboard drawings on the Steiner model and was particularly absorbed in the social and ethical implications of Steiner’s thought. … But these days any talk about ”the spiritual in art” tends to make everyone squirm a little. … And yet the impulse to seek a content in art that amounts to something beyond yet another new twist on yesterday’s new twist continues to find adherents. The programmatic philosophy that spawned Steiner’s blackboard drawings may attract a limited audience. But the drawings themselves, with their modest formal beauties tied to an ambitious vision, offer a kind of art — an uncool, un-Duchampian esthetic, let’s call it, one often associated with ”outsider art” today — that will have its appeal.
I’m quite fond of this drawing, from a lecture on September 19, 1924, ‘Speech and Drama’ (GA 282):
His words: “The impression of something living, something realistic, is produced by the fact that when we look at the stage image we see there has arisen in living imagination from decanted dreams.” (Source.)