This is from a recent anthroposophical publication (‘being human’). It starts with a quote by author and anthroposophist Andrei Belyi.
‘“He had, as it were, a therapeutic smile: the countenance blossomed… One felt that one had nothing of the kind to give in return. He had the gift of the smile, the faculty of direct expression from the heart… His smile could have had a smothering effect had he not tempered it down when necessary. Many know his sunny smile; we spoke of it. One must speak about it, for not a single photograph of his reflects it.”
‘This latter sentence has bothered us anthroposophists ever since we realized this sad fact. An old anthroposophist told me that there was an esoteric reason for Steiner’s deliberate non-smiling poses, but I do feel that we have lost a wonderful aspect of him because we have never seen his smile. We have a faint glimmer of the angelic charm of his smile in this sole photograph from Steiner’s childhood, which was taken when he was about six.’
Souce [pdf]. (The rest of the article is about archangels.)