He refers to the fall of Borders books -- "reminding me of what Silk said about Brill in The Belgariad after throwing him off a cliff:
‘What was that?’ Belgarath asked.
‘Brill,’ Silk replied blandly.
‘Again? What was he doing this time?’
‘Trying to fly, last time I saw him.’
The old man looked puzzled.
‘He wasn’t doing it very well,’ Silk added.
Belgarath shrugged. ‘Maybe it will come to him in time.’
. . . . From far below — terribly far below — there came a faint, muffled crash; then, after several seconds, another. ‘Does bouncing count?’ Silk asked.
‘Then I’d say he didn’t learn in time.’"