The Puranas repeatedly teach that the moon is larger than the sun:
Brahmanda Purana - Book 2, Chapter 21
7 The extent of the disc of the sun is nine thousand Yojanas. Its girth is three times the extent.
8 In diameter as well as girth (Circumference), the moon is twice as much as the sun.
Linga Purana - Book 1, Chapter 61
28 The diameter of the sun is nine thousand yojanas. The extent of its circular surface is three times that.
29 The extent of the moon is twice that of the sun. Rāhu assumes a form equal to both of them and moves about beneath them.
Matsya Purana - Chapter 124
5 I shall again and again impress on you the vast magnitude of the sun and the moon.
6 On account of the vastness of their magnitude, the expression mahat (Great) has been used in their connection.
7 The circumference of the sun is equal to the diameter of the Bharatavarsa. It is 9,000 yojnas in diameter and three times as much in circumference.
8 The moon is twice as much bigger in circumference and diameter than the sun.
Vayu Purana - Book 1, Chapter 50
63 The extent of the sun is nine thousand Yojanas. The girth or the extent of its disc is thrice its diameter. The lunar disc is twice the solar disc (in diameter as well as girth).
Vayu Purana - Book 1, Chapter 53
61 The planets are brightly illuminated due to their contact with the rays of the Sun. The diameter of the Sun is nine thousand Yojanas.
62 The girth of the Sun is three times its diameter. The width of the Moon is twice that of the Sun.
In addition to the Puranas getting the sun and moon's size relative to each other wrong, they also get the absolute sizes of each wrong, if "yojanas" is to have any normative meaning. A "yojana" is traditionally said to be around 10 miles. This would mean the sun, at 9,000 yojonas, would be around 90,000 miles in diameter (actual size 865,000 miles), and the moon, at twice the diameter of the sun, would be 18,000 yojanas, or 180,000 miles (actual size 2,159 miles).
Therefore, this is another instance of scientific error in Hindu scripture.