Brahma and VishhNu wanted to measure your wealth i.e.greatness

तवैश्वर्यं यत्नाद्‌ यदुपरि विरिञ्चिर्हरिरधः
परिच्छेतुं यातावनलमनलस्कन्धवपुषः।
ततो भक्तिश्रद्धा-भरगुरु-गृणद्भ्यां गिरिश यत्‌
स्वयं तस्थे ताभ्यां तव किमनुवृत्तिर्न फलति॥ १०॥

Brahma and VishhNu wanted to measure your wealth i.e.greatness . You took the form of Fire and your whole body was a column of fire extending over space . While Brahma took the form of a swan and flew high to see the top(head), VishhNu took the form of a boar and dug up downwards to see the bottom (feet).Neither could succeed.(While VishhNu confessed the truth, Brahma falsely claimed that he had found the top and persuaded the Ketaki flower to bear false witness.Shiva punished Brahma by removing one of his 5 heads and ordered that henceforth the Ketaki flower should not be used for his worship).When ultimately both praised you with full devotion and faith, you stood before them revealing your normal form . O, mountain-dweller, does not toeing your line always bear fruit? .