Maybe it could refer to either the poet or the sun throughout the entire line, if you think of the mantle blue as being the actual sky that the sun is able to twitch over his shoulder.

或者两者皆可,从整句的行文看来，如果你们把蓝色的丝巾看作是真实的天空的话,那么太阳的确是能够在他的肩上轻轻颤动。

耶鲁公开课 - 弥尔顿课程节选

Well,if it's not one,and not the other,what are the remaining possibilities?

如果两者皆非，还有其他什么可能？

耶鲁公开课 - 死亡课程节选

These constitute two irreconcilable alternatives, two different callings, so to speak, and any attempt, I think, to reconcile or to synthesize these two can only lead to a deep injustice to each.

这包含了两种无法调和的准则，两种不同的召唤，可以说任何想要，调和或综合两者的意图,仅会导致双方皆产生深度的不义。

耶鲁公开课 - 政治哲学导论课程节选