Definition of "thoughtful"

Now the New Year reviving old Desires,The thoughtful Soul to Solitude retires,Where the White Hand of Moses on the BoughPuts out, and Jesus from the Ground suspires.

1859, Edward Fitzgerald, The Rubáiyát of Omar Khayyám: The Astronomer-Poet of Persia, page 2

But Richmond, his grandfather's darling, after one thoughtful glance cast under his lashes at that uncompromising countenance appeared to lose himself in his own reflections.

1959, Georgette Heyer, chapter 1, in The Unknown Ajax