As I have mentioned before, Einstein (perhaps surprisingly) was a close friend of King Albert I and Queen Elisabeth of Belgium. He shared with the Queen a passion for classical music, and enjoyed discussing political and philosophical issues with the King. Many fascinating and touching letters between Einstein and the royal couple testify to the depth of their mutual regard (for example, see HERE). The King and Queen were both very anxious for Einstein's safety in the face of Nazi persecution. When he spent time at the seaside resort of Le Coq, Belgium, in 1933, Albert insisted on providing him with two bodyguards to protect him day and night.
Einstein and Elisabeth enjoyed exchanging rhymed greetings. Here is one, dated March 15, 1933, by the Queen. Playing on the scientist's name, (ein stein = "one stone") she alluded to her fears for his safety. Einstein had previously written her a poem, regretting his inability to visit the royal couple. He had compared himself to a tree:
It sends- its greetings to convey-
A twig, for it itself must stay.
The Queen's reply, I think, is very charming:
The twig the greeting did convey
From the tree that had to stay,
And from the friend, whose heart so big
Could send great joy by tiny twig.
A thousand thanks aloud I cry
Unto mountain, sea and sky.
Now, when stones begin to shake,
I pray ONE STONE no harm will take.
(cited in Albert Einstein: The Human Side, 1981, p. 49)