This sabian symbol immediately makes me think of the 4 of Wands card. It's actually interesting since wands often represent the element of FIRE, which is also the astrological element of Aries.
Also, the thought of the hammock being "empty" makes me smile, because most Arians (as Aries people are known) tend to be very active and energetic, so it's not likely for one to find an Arian resting in a hammock, when there's so much of the world to conquer!
But the symbol COULD indicate the rest to be had AFTER one has accomplished their goals in the world.
Another thought based on nothing more than my own imagination and what my friends call my "weird tarot math," which somehow always seems to make sense, is this: the only time Aries will fall on the 18th (per the degrees of this symbol) is in April. According to my weird tarot mathematics: April 18 (sun sign, Aries) can also be seen as the 18th of the 4th month, or 4/18. If you add 4+1+8=13...and 1+3=4. This brings us back to the tarot card this symbol reminds me of, *4* of Wands! In addition, the number "4" in the minor arcana of the tarot is often representative of some sort of rest or stillness (4 Wands, 4 cups, 4 swords, 4 pentacles)...which brings my thought full circle: the symbol here seems to indicate "rest"...going back to the #4! Oh, AND, one more thought which can build on the numerological feat
D) I just performed is that the 4th card of the major arcana is The Emperor, often associated with the astrological sign of Aries! Hey now! My tarot math just came full circle! Yessss!
Isn't that a cool and round about way of thinking of numbers for someone as mathematically challenged as myself?!
GA